diff --git a/.gitignore b/.gitignore
index fc80547..75e8162 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,6 @@ Cargo.lock
 
 # .dot file for tests
 **/*.dot
+
+# Editor related configuratigurations
+.vscode
\ No newline at end of file
diff --git a/src/arrow.rs b/src/arrow.rs
index 9663fa1..14e9a85 100644
--- a/src/arrow.rs
+++ b/src/arrow.rs
@@ -1,4 +1,3 @@
-
 /// This structure holds all information that can describe an arrow connected to
 /// either start or end of an edge.
 #[derive(Clone, Hash, PartialEq, Eq)]
@@ -16,9 +15,7 @@ impl Arrow {
 
     /// Arrow constructor which returns a default arrow
     pub fn default() -> Arrow {
-        Arrow {
-            arrows: vec![],
-        }
+        Arrow { arrows: vec![] }
     }
 
     /// Arrow constructor which returns an empty arrow
@@ -31,7 +28,7 @@ impl Arrow {
     /// Arrow constructor which returns a regular triangle arrow, without modifiers
     pub fn normal() -> Arrow {
         Arrow {
-            arrows: vec![ArrowShape::normal()]
+            arrows: vec![ArrowShape::normal()],
         }
     }
 
@@ -47,12 +44,11 @@ impl Arrow {
         let mut cow = String::new();
         for arrow in &self.arrows {
             cow.push_str(&arrow.to_dot_string());
-        };
+        }
         cow
     }
 }
 
-
 impl Into<Arrow> for [ArrowShape; 2] {
     fn into(self) -> Arrow {
         Arrow {
@@ -103,14 +99,13 @@ pub enum Side {
 impl Side {
     pub fn as_slice(self) -> &'static str {
         match self {
-            Side::Left  => "l",
+            Side::Left => "l",
             Side::Right => "r",
-            Side::Both  => "",
+            Side::Both => "",
         }
     }
 }
 
-
 /// This enumeration represents all possible arrow edge
 /// as defined in [grapviz documentation](http://www.graphviz.org/content/arrow-shapes).
 #[derive(Clone, Copy, Hash, PartialEq, Eq)]
@@ -199,37 +194,37 @@ impl ArrowShape {
     pub fn to_dot_string(&self) -> String {
         let mut res = String::new();
         match *self {
-            Box(fill, side) | ICurve(fill, side)| Diamond(fill, side) |
-            Inv(fill, side) | Normal(fill, side)=> {
+            Box(fill, side)
+            | ICurve(fill, side)
+            | Diamond(fill, side)
+            | Inv(fill, side)
+            | Normal(fill, side) => {
                 res.push_str(fill.as_slice());
                 match side {
                     Side::Left | Side::Right => res.push_str(side.as_slice()),
-                    Side::Both => {},
+                    Side::Both => {}
                 };
-            },
-            Dot(fill)       => res.push_str(fill.as_slice()),
-            Crow(side) | Curve(side) | Tee(side)
-            | Vee(side) => {
-                match side {
-                    Side::Left | Side::Right => res.push_str(side.as_slice()),
-                    Side::Both => {},
-                }
             }
-            NoArrow => {},
+            Dot(fill) => res.push_str(fill.as_slice()),
+            Crow(side) | Curve(side) | Tee(side) | Vee(side) => match side {
+                Side::Left | Side::Right => res.push_str(side.as_slice()),
+                Side::Both => {}
+            },
+            NoArrow => {}
         };
         match *self {
-            NoArrow         => res.push_str("none"),
-            Normal(_, _)    => res.push_str("normal"),
-            Box(_, _)       => res.push_str("box"),
-            Crow(_)         => res.push_str("crow"),
-            Curve(_)        => res.push_str("curve"),
-            ICurve(_, _)    => res.push_str("icurve"),
-            Diamond(_, _)   => res.push_str("diamond"),
-            Dot(_)          => res.push_str("dot"),
-            Inv(_, _)       => res.push_str("inv"),
-            Tee(_)          => res.push_str("tee"),
-            Vee(_)          => res.push_str("vee"),
+            NoArrow => res.push_str("none"),
+            Normal(_, _) => res.push_str("normal"),
+            Box(_, _) => res.push_str("box"),
+            Crow(_) => res.push_str("crow"),
+            Curve(_) => res.push_str("curve"),
+            ICurve(_, _) => res.push_str("icurve"),
+            Diamond(_, _) => res.push_str("diamond"),
+            Dot(_) => res.push_str("dot"),
+            Inv(_, _) => res.push_str("inv"),
+            Tee(_) => res.push_str("tee"),
+            Vee(_) => res.push_str("vee"),
         };
         res
     }
-}
\ No newline at end of file
+}
diff --git a/src/edge.rs b/src/edge.rs
index 814fa3d..2faa389 100644
--- a/src/edge.rs
+++ b/src/edge.rs
@@ -1,8 +1,4 @@
-use crate::{
-    arrow::{Arrow},
-    style::{Style},
-    utils::{quote_string},
-};
+use crate::{arrow::Arrow, style::Style, utils::quote_string};
 
 /// `Graph`'s edge.
 #[derive(Clone)]
@@ -10,6 +6,8 @@ pub struct Edge {
     from: String,
     to: String,
     label: String,
+    label_url: String,
+    url: String,
     style: Style,
     start_arrow: Arrow,
     end_arrow: Arrow,
@@ -18,40 +16,55 @@ pub struct Edge {
 
 impl Edge {
     pub fn new(from: &str, to: &str, label: &str) -> Self {
-        Edge { from: String::from(from), to: String::from(to), label: String::from(label), style: Style::None, start_arrow: Arrow::default(), end_arrow: Arrow::default(), color: None }
+        Edge {
+            from: String::from(from),
+            to: String::from(to),
+            label: String::from(label),
+            label_url: Default::default(),
+            color: None,
+            style: Style::None,
+            start_arrow: Arrow::default(),
+            end_arrow: Arrow::default(),
+            url: Default::default(),
+        }
     }
 
-    pub fn label(&mut self, label: &str) -> Self {
-        let mut edge = self.clone();
-        edge.label = String::from(label);
-        edge
+    pub fn label(mut self, label: &str) -> Self {
+        self.label = String::from(label);
+        self
     }
 
-    pub fn style(&mut self, style: Style) -> Self {
-        let mut edge = self.clone();
-        edge.style = style;
-        edge
+    pub fn style(mut self, style: Style) -> Self {
+        self.style = style;
+        self
     }
 
-    pub fn color(&mut self, color: Option<&str>) -> Self {
-        let mut edge = self.clone();
-        edge.color = match color {
+    pub fn color(mut self, color: Option<&str>) -> Self {
+        self.color = match color {
             Some(c) => Some(String::from(c)),
-            None => None
+            None => None,
         };
-        edge
+        self
+    }
+
+    pub fn start_arrow(mut self, arrow: Arrow) -> Self {
+        self.start_arrow = arrow;
+        self
     }
 
-    pub fn start_arrow(&mut self, arrow: Arrow) -> Self {
-        let mut edge = self.clone();
-        edge.start_arrow = arrow;
-        edge
+    pub fn end_arrow(mut self, arrow: Arrow) -> Self {
+        self.end_arrow = arrow;
+        self
     }
 
-    pub fn end_arrow(&mut self, arrow: Arrow) -> Self {
-        let mut edge = self.clone();
-        edge.end_arrow = arrow;
-        edge
+    pub fn label_url(mut self, url: String) -> Self {
+        self.label_url = url;
+        self
+    }
+
+    pub fn url(mut self, url: String) -> Self {
+        self.url = url;
+        self
     }
 
     pub fn to_dot_string(&self, edge_symbol: &str) -> String {
@@ -59,15 +72,36 @@ impl Edge {
         let escaped_label: &String = &quote_string(self.label.clone());
         let start_arrow_s: String = self.start_arrow.to_dot_string();
         let end_arrow_s: String = self.end_arrow.to_dot_string();
+        let escaped_label_url: &String = &quote_string(self.label_url.clone());
+        let escaped_url: &String = &quote_string(self.url.clone());
 
-        let mut text = vec!["\"", self.from.as_str(), "\" ",
-                            edge_symbol, " ",
-                            "\"", self.to.as_str(), "\"",];
+        let mut text = vec![
+            "\"",
+            self.from.as_str(),
+            "\" ",
+            edge_symbol,
+            " ",
+            "\"",
+            self.to.as_str(),
+            "\"",
+        ];
 
         text.push("[label=");
         text.push(escaped_label.as_str());
         text.push("]");
 
+        if !self.label_url.is_empty() {
+            text.push("[labelURL=");
+            text.push(escaped_label_url.as_str());
+            text.push("]");
+        }
+
+        if !self.url.is_empty() {
+            text.push("[URL=");
+            text.push(escaped_url.as_str());
+            text.push("]");
+        }
+
         if self.style != Style::None {
             text.push("[style=\"");
             text.push(self.style.as_slice());
@@ -75,9 +109,7 @@ impl Edge {
         }
 
         let color: Option<String> = match &self.color {
-            Some(l) => {
-                Some((*l).clone())
-            },
+            Some(l) => Some((*l).clone()),
             None => None,
         };
         if let Some(c) = color {
@@ -91,10 +123,18 @@ impl Edge {
         let mut arrow_str: String = String::new();
         if !self.start_arrow.is_default() || !self.end_arrow.is_default() {
             if !self.end_arrow.is_default() {
-                arrow_text.push(vec!["arrowhead=\"", &end_arrow_s, "\""].into_iter().collect());
+                arrow_text.push(
+                    vec!["arrowhead=\"", &end_arrow_s, "\""]
+                        .into_iter()
+                        .collect(),
+                );
             }
             if !self.start_arrow.is_default() {
-                arrow_text.push(vec!["arrowtail=\"", &start_arrow_s, "\""].into_iter().collect());
+                arrow_text.push(
+                    vec!["arrowtail=\"", &start_arrow_s, "\""]
+                        .into_iter()
+                        .collect(),
+                );
             }
             if !self.start_arrow.is_default() && !self.end_arrow.is_default() {
                 arrow_text.push(String::from("dir=\"both\""));
@@ -110,4 +150,4 @@ impl Edge {
         text.push(";");
         return text.into_iter().collect();
     }
-}
\ No newline at end of file
+}
diff --git a/src/graph.rs b/src/graph.rs
index feaee1f..8a57259 100644
--- a/src/graph.rs
+++ b/src/graph.rs
@@ -1,22 +1,28 @@
-use crate::{
-    node::{Node},
-    edge::{Edge}, subgraph::Subgraph,
-};
-use std::io::prelude::*;
+use crate::{edge::Edge, node::Node, subgraph::Subgraph, utils::quote_string};
 use std::io;
+use std::io::prelude::*;
 
 /// Entry point of this library, use `to_dot_string` to get the string output.
+#[derive(Clone)]
 pub struct Graph {
     name: String,
     kind: Kind,
+    url: String,
     nodes: Vec<Node>,
     edges: Vec<Edge>,
-    subgraph: Vec<Subgraph>
+    subgraph: Vec<Subgraph>,
 }
 
 impl Graph {
     pub fn new(name: &str, kind: Kind) -> Graph {
-        Graph { name: String::from(name), kind: kind, nodes: vec![], edges: vec![], subgraph: vec![] }
+        Graph {
+            name: String::from(name),
+            kind: kind,
+            nodes: vec![],
+            edges: vec![],
+            subgraph: vec![],
+            url: Default::default(),
+        }
     }
 
     pub fn add_node(&mut self, node: Node) -> () {
@@ -31,6 +37,12 @@ impl Graph {
         self.subgraph.push(subgraph.edgeop(self.kind.edgeop()))
     }
 
+    pub fn url(&mut self, url: String) -> Self {
+        let mut graph = self.clone();
+        graph.url = url;
+        graph
+    }
+
     pub fn to_dot_string(&self) -> io::Result<String> {
         let mut writer = Vec::new();
         self.render_opts(&mut writer).unwrap();
@@ -41,11 +53,7 @@ impl Graph {
 
     /// Renders graph `g` into the writer `w` in DOT syntax.
     /// (Main entry point for the library.)
-    fn render_opts<'a,
-                    W: Write>
-        (&self,
-        w: &mut W)
-        -> io::Result<()> {
+    fn render_opts<'a, W: Write>(&self, w: &mut W) -> io::Result<()> {
         fn writeln<W: Write>(w: &mut W, arg: &[&str]) -> io::Result<()> {
             for &s in arg {
                 w.write_all(s.as_bytes())?;
@@ -58,6 +66,12 @@ impl Graph {
         }
 
         writeln(w, &[self.kind.keyword(), " ", self.name.as_str(), " {"])?;
+
+        if !self.url.is_empty() {
+            indent(w)?;
+            writeln(w, &["URL=", quote_string(self.url.clone()).as_str()])?;
+        }
+
         for n in self.subgraph.iter() {
             indent(w)?;
             let mut text: Vec<&str> = vec![];
@@ -101,7 +115,7 @@ impl Kind {
     pub fn keyword(&self) -> &'static str {
         match *self {
             Kind::Digraph => "digraph",
-            Kind::Graph => "graph"
+            Kind::Graph => "graph",
         }
     }
 
@@ -112,4 +126,4 @@ impl Kind {
             Kind::Graph => "--",
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/lib.rs b/src/lib.rs
index 0124db8..a8aabdc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,18 +5,18 @@
 // except according to those terms.
 
 //! A library for generating Graphviz DOT language files.
-//! 
+//!
 //! The very basic three parts of a DOT file and in this library is `Graph`,
 //! `Node` and `Edge`. `Graph` is the entry point of the library. You could
 //! generate an empty graph .dot file by simply use:
-//! 
+//!
 //! ```rust
 //! use dot_graph::{Graph, Kind};
-//! 
+//!
 //! let graph = Graph::new("empty_graph", Kind::Digraph);
-//! 
+//!
 //! let dot_string = graph.to_dot_string().unwrap();
-//! 
+//!
 //! assert_eq!(dot_string,
 //!    r#"digraph empty_graph {
 //! }
@@ -24,18 +24,18 @@
 //! ```
 //!
 //! In order to add some basic nodes and edges:
-//! 
+//!
 //! ```rust
 //! use dot_graph::{Graph, Kind, Node, Edge};
-//! 
+//!
 //! let mut graph = Graph::new("single_edge", Kind::Digraph);
-//! 
+//!
 //! graph.add_node(Node::new("N0"));
 //! graph.add_node(Node::new("N1"));
 //! graph.add_edge(Edge::new("N0", "N1", "E"));
-//! 
+//!
 //! let dot_string = graph.to_dot_string().unwrap();
-//! 
+//!
 //! assert_eq!(dot_string,
 //! r#"digraph single_edge {
 //!     "N0"[label="N0"];
@@ -44,19 +44,19 @@
 //! }
 //! "#);
 //! ```
-//! 
+//!
 //! If you want add some more attributes, like style, arrow, color,
 //! you could call these methods in a chain, like:
-//! 
+//!
 //! ```rust
 //! use dot_graph::{Graph, Kind, Node, Edge, Style};
-//! 
+//!
 //! let mut graph = Graph::new("single_edge", Kind::Digraph);
-//! 
+//!
 //! graph.add_node(Node::new("N0"));
 //! graph.add_node(Node::new("N1"));
 //! graph.add_edge(Edge::new("N0", "N1", "E").style(Style::Bold).color(Some("red")));
-//! 
+//!
 //! assert_eq!(graph.to_dot_string().unwrap(),
 //! r#"digraph single_edge {
 //!     "N0"[label="N0"];
@@ -65,9 +65,9 @@
 //! }
 //! "#);
 //! ```
-//! 
+//!
 //! After version 0.2.1, dot_graph support subgraph generation, for example:
-//! 
+//!
 //! ```rust
 //! #[test]
 //! fn test_subgraph() {
@@ -85,7 +85,7 @@
 //!     graph.add_edge(Edge::new("N1", "N3", ""));
 //!     graph.add_edge(Edge::new("N2", "N3", ""));
 //!     
-//! 
+//!
 //!     assert_eq!(graph.to_dot_string().unwrap(),
 //! r#"digraph di {
 //! subgraph cluster_0 {
@@ -106,30 +106,29 @@
 //! "#);
 //! }
 //! ```
-//! 
+//!
 //! For more examples, please check the tests.
-//! 
+//!
 //! The library is under active development, we'll include more dot attributes
 //! in the future.
-//! 
+//!
 //! # References
 //!
 //! * [Graphviz](http://graphviz.org/)
 //!
 //! * [DOT language](http://graphviz.org/doc/info/lang.html)
 
-mod style;
 mod arrow;
-mod node;
 mod edge;
 mod graph;
-mod utils;
+mod node;
+mod style;
 mod subgraph;
+mod utils;
 
-pub use style::Style;
-pub use arrow::{Arrow, ArrowShape, Side, Fill};
-pub use node::{Node};
-pub use edge::{Edge};
+pub use arrow::{Arrow, ArrowShape, Fill, Side};
+pub use edge::Edge;
 pub use graph::{Graph, Kind};
+pub use node::Node;
+pub use style::Style;
 pub use subgraph::Subgraph;
-
diff --git a/src/node.rs b/src/node.rs
index efbc6f6..ff4b838 100644
--- a/src/node.rs
+++ b/src/node.rs
@@ -1,10 +1,6 @@
 /// each node is an index in a vector in the graph.
 // pub type Node = usize;
-
-use crate::{
-    style::Style,
-    utils::{quote_string},
-};
+use crate::{style::Style, utils::quote_string};
 
 /// `Graph`'s node
 #[derive(Clone)]
@@ -13,56 +9,72 @@ pub struct Node {
     label: String,
     style: Style,
     color: Option<String>,
-    shape: Option<String>
+    shape: Option<String>,
+    url: String,
 }
 
 impl Node {
     pub fn new(name: &str) -> Self {
-        Node { name: new_name(name), label: String::from(name), style: Style::None, color: None, shape: None }
+        Node {
+            name: new_name(name),
+            label: String::from(name),
+            style: Style::None,
+            color: None,
+            shape: None,
+            url: Default::default(),
+        }
     }
 
-    pub fn label(&self, label: &str) -> Self {
-        let mut node = self.clone();
-        node.label = String::from(label);
-        node
+    pub fn label(mut self, label: &str) -> Self {
+        self.label = String::from(label);
+        self
     }
 
-    pub fn style(&self, style: Style) -> Self {
-        let mut node = self.clone();
-        node.style = style;
-        node
+    pub fn style(mut self, style: Style) -> Self {
+        self.style = style;
+        self
     }
 
-    pub fn shape(&self, shape: Option<&str>) -> Self {
-        let mut node = self.clone();
+    pub fn shape(mut self, shape: Option<&str>) -> Self {
         match shape {
-            Some(s) => node.shape = Some(String::from(s)),
-            None => node.shape = None
+            Some(s) => self.shape = Some(String::from(s)),
+            None => self.shape = None,
         }
-        node
+        self
     }
 
-    pub fn color(&self, color: Option<&str>) -> Self {
-        let mut node = self.clone();
-        node.color = match color {
+    pub fn color(mut self, color: Option<&str>) -> Self {
+        self.color = match color {
             Some(c) => Some(String::from(c)),
-            None => None
+            None => None,
         };
-        node
+        self
+    }
+
+    pub fn url(mut self, url: String) -> Self {
+        self.url = url;
+        self
     }
 
     pub fn to_dot_string(&self) -> String {
         let colorstring: String;
 
-        let escaped: String = quote_string(self.label.clone());
+        let escaped_label: String = quote_string(self.label.clone());
+        let escaped_url: String = quote_string(self.url.clone());
         let shape: String;
 
         let mut text = vec!["\"", self.name.as_str(), "\""];
 
         text.push("[label=");
-        text.push(escaped.as_str());
+        text.push(escaped_label.as_str());
         text.push("]");
 
+        if !self.url.is_empty() {
+            text.push("[URL=");
+            text.push(escaped_url.as_str());
+            text.push("]");
+        }
+
         if self.style != Style::None {
             text.push("[style=\"");
             text.push(self.style.as_slice());
@@ -86,7 +98,6 @@ impl Node {
         text.push(";");
         return text.into_iter().collect();
     }
-
 }
 
 /// Check if the node's name is illegal.
@@ -112,7 +123,7 @@ fn new_name(name: &str) -> String {
     if !chars.all(is_constituent) {
         panic!("The name of the node should only contain letter/number/underscore/dot")
     }
-        return String::from(name);
+    return String::from(name);
 
     fn is_letter_or_underscore_or_dot(c: char) -> bool {
         in_range('a', c, 'z') || in_range('A', c, 'Z') || c == '_' || c == '.'
@@ -123,4 +134,4 @@ fn new_name(name: &str) -> String {
     fn in_range(low: char, c: char, high: char) -> bool {
         low as usize <= c as usize && c as usize <= high as usize
     }
-}
\ No newline at end of file
+}
diff --git a/src/style.rs b/src/style.rs
index eeb36a6..0694601 100644
--- a/src/style.rs
+++ b/src/style.rs
@@ -32,4 +32,4 @@ impl Style {
             Style::Wedged => "wedged",
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/subgraph.rs b/src/subgraph.rs
index fdff9c6..6c4c9ec 100644
--- a/src/subgraph.rs
+++ b/src/subgraph.rs
@@ -1,9 +1,4 @@
-use crate::{
-    node::Node,
-    style::Style,
-    utils::quote_string, Edge,
-    Kind
-};
+use crate::{node::Node, style::Style, utils::quote_string, Edge, Kind};
 
 /// `Graph`'s subgraph
 #[derive(Clone)]
@@ -15,11 +10,21 @@ pub struct Subgraph {
     style: Style,
     color: Option<String>,
     edgeop: String,
+    url: String,
 }
 
 impl Subgraph {
     pub fn new(name: &str) -> Self {
-        Subgraph { name: new_name(name), nodes: vec![], edges: vec![], label: String::new(), style: Style::None, color: None, edgeop: String::from(Kind::Digraph.edgeop())}
+        Subgraph {
+            name: new_name(name),
+            nodes: vec![],
+            edges: vec![],
+            label: String::new(),
+            style: Style::None,
+            color: None,
+            edgeop: String::from(Kind::Digraph.edgeop()),
+            url: Default::default(),
+        }
     }
 
     pub fn add_node(&mut self, node: Node) -> () {
@@ -34,36 +39,45 @@ impl Subgraph {
         self.edges.push(edge);
     }
 
-    pub fn label(&self, label: &str) -> Self {
-        let mut subg = self.clone();
-        subg.label = String::from(label);
-        subg
+    pub fn label(mut self, label: &str) -> Self {
+        self.label = String::from(label);
+        self
     }
 
-    pub fn style(&self, style: Style) -> Self {
-        let mut subg = self.clone();
-        subg.style = style;
-        subg
+    pub fn style(mut self, style: Style) -> Self {
+        self.style = style;
+        self
     }
 
-    pub fn color(&self, color: Option<&str>) -> Self {
-        let mut subg = self.clone();
-        subg.color = match color {
+    pub fn color(mut self, color: Option<&str>) -> Self {
+        self.color = match color {
             Some(c) => Some(String::from(c)),
-            None => None
+            None => None,
         };
-        subg
+        self
+    }
+
+    pub fn edgeop(mut self, edgeop: &str) -> Self {
+        self.edgeop = String::from(edgeop);
+        self
     }
 
-    pub fn edgeop(&self, edgeop: &str) -> Self {
-        let mut subg = self.clone();
-        subg.edgeop = String::from(edgeop);
-        subg
+    pub fn url(mut self, url: String) -> Self {
+        self.url = url;
+        self
     }
 
     pub fn to_dot_string(&self) -> String {
         let mut text = vec!["subgraph ", self.name.as_str(), " {\n        "];
 
+        let escaped_url: String;
+        if !self.url.is_empty() {
+            escaped_url = quote_string(self.url.clone());
+            text.push("URL=");
+            text.push(escaped_url.as_str());
+            text.push(";\n        ");
+        }
+
         text.push("label=\"");
         text.push(self.label.as_str());
         text.push("\";\n    ");
@@ -82,7 +96,8 @@ impl Subgraph {
             text.push(";\n    ");
         }
 
-        let subgraph_node_names = self.nodes
+        let subgraph_node_names = self
+            .nodes
             .iter()
             .map(|n| n.to_dot_string())
             .collect::<Vec<String>>()
@@ -93,10 +108,10 @@ impl Subgraph {
             text.push(&subgraph_node_names);
             text.push("\n    ");
         }
-        
 
         let edge_symbol = &self.edgeop;
-        let subgraph_edge_strs = self.edges
+        let subgraph_edge_strs = self
+            .edges
             .iter()
             .map(|e| e.to_dot_string(&edge_symbol))
             .collect::<Vec<String>>()
@@ -109,9 +124,7 @@ impl Subgraph {
         }
 
         text.push("}");
-        
 
-        
         return text.into_iter().collect();
     }
 }
@@ -143,7 +156,7 @@ fn new_name(name: &str) -> String {
     if !name.starts_with("cluster_") {
         panic!("The name of the subgraph should start with \"cluster_\"")
     }
-        return String::from(name);
+    return String::from(name);
 
     fn is_letter_or_underscore(c: char) -> bool {
         in_range('a', c, 'z') || in_range('A', c, 'Z') || c == '_'
@@ -154,4 +167,4 @@ fn new_name(name: &str) -> String {
     fn in_range(low: char, c: char, high: char) -> bool {
         low as usize <= c as usize && c as usize <= high as usize
     }
-}
\ No newline at end of file
+}
diff --git a/src/utils.rs b/src/utils.rs
index b2c5056..6092f6a 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -1,3 +1,3 @@
 pub fn quote_string(s: String) -> String {
     format!("\"{}\"", s)
-}
\ No newline at end of file
+}
diff --git a/tests/integration.rs b/tests/integration.rs
index 10632e4..90fcc04 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -28,6 +28,19 @@ r#"digraph single_node {
 "#);
     }
 
+    #[test]
+    fn single_node_with_url() {
+        let mut graph = Graph::new("single_node", Kind::Digraph).url("https://example.com/".into());
+        let node = Node::new("N0").url("https://example.com/".into());
+        graph.add_node(node);
+        assert_eq!(graph.to_dot_string().unwrap(),
+r#"digraph single_node {
+    URL="https://example.com/"
+    "N0"[label="N0"][URL="https://example.com/"];
+}
+"#);
+    }
+
     #[test]
     fn dot_in_node_name() {
         let mut graph = Graph::new("single_node", Kind::Digraph);
@@ -249,7 +262,7 @@ r#"graph g {
         let mut c1 = Subgraph::new("cluster_0").label("");
         c1.add_node(Node::new("N0"));
         c1.add_node(Node::new("N1"));
-        let mut c2 = Subgraph::new("cluster_1").label("");
+        let mut c2 = Subgraph::new("cluster_1").url("https://example.com/".into()).label("");
         c2.add_node(Node::new("N2"));
         c2.add_node(Node::new("N3"));
         graph.add_subgraph(c1);
@@ -268,6 +281,7 @@ r#"digraph di {
         "N1"[label="N1"];
     }
     subgraph cluster_1 {
+        URL="https://example.com/";
         label="";
         "N2"[label="N2"];
         "N3"[label="N3"];
@@ -420,4 +434,52 @@ r#"digraph G {
         let result = graph.to_dot_string();
         result.unwrap();
     }
+
+    #[test]
+    fn single_edge_with_url() {
+        let mut graph = Graph::new("single_edge", Kind::Digraph);
+        graph.add_node(Node::new("N0"));
+        graph.add_node(Node::new("N1"));
+        graph.add_edge(Edge::new("N0", "N1", "E").url("https://example.com/".into()));
+        assert_eq!(graph.to_dot_string().unwrap(),
+r#"digraph single_edge {
+    "N0"[label="N0"];
+    "N1"[label="N1"];
+    "N0" -> "N1"[label="E"][URL="https://example.com/"];
+}
+"#);
+    }
+
+    #[test]
+    fn single_edge_with_label_url() {
+        let mut graph = Graph::new("single_edge", Kind::Digraph);
+        graph.add_node(Node::new("N0"));
+        graph.add_node(Node::new("N1"));
+        graph.add_edge(Edge::new("N0", "N1", "E").label_url("https://example.com/".into()));
+        assert_eq!(graph.to_dot_string().unwrap(),
+r#"digraph single_edge {
+    "N0"[label="N0"];
+    "N1"[label="N1"];
+    "N0" -> "N1"[label="E"][labelURL="https://example.com/"];
+}
+"#);
+    }
+
+    #[test]
+    fn single_edge_with_label_url_and_url() {
+        let mut graph = Graph::new("single_edge", Kind::Digraph);
+        graph.add_node(Node::new("N0"));
+        graph.add_node(Node::new("N1"));
+        graph.add_edge(Edge::new("N0", "N1", "E")
+            .url("https://example.com/".into())
+            .label_url("https://example.com/".into())
+        );
+        assert_eq!(graph.to_dot_string().unwrap(),
+r#"digraph single_edge {
+    "N0"[label="N0"];
+    "N1"[label="N1"];
+    "N0" -> "N1"[label="E"][labelURL="https://example.com/"][URL="https://example.com/"];
+}
+"#);
+    }
 }
\ No newline at end of file