diff --git a/README.md b/README.md
index dab5cac..dee5ed4 100644
--- a/README.md
+++ b/README.md
@@ -20,12 +20,12 @@ npm install api-problem
 
 ### Constructor: `Problem(status[, title][, type][, members])`
 
-| name          | type     | required | default            | description                                                                            | referece                    |
-|---------------|----------|----------|--------------------|----------------------------------------------------------------------------------------|-----------------------------|
-| **`status`**  | `String` | `✔`      | `N/A`              | The HTTP status code generated by the origin server for this occurrence of the problem | \[Section 3.1\]\[spec-3.1\] |
-| **`title`**   | `String` | `✖`      | HTTP status phrase | A short, human-readable summary of the problem type                                    | \[Section 3.1\]\[spec-3.1\] |
-| **`type`**    | `String` | `✖`      | `about:blank`      | A URI reference that identifies the problem type                                       | \[Section 3.1\]\[spec-3.1\] |
-| **`details`** | `Object` | `✖`      | `N/A`              | additional details to attach to object                                                 | \[Section 3.1\]\[spec-3.2\] |
+| name          | type     | required | default            | description                                                                            | referece                                                       |
+|---------------|----------|----------|--------------------|----------------------------------------------------------------------------------------|----------------------------------------------------------------|
+| **`status`**  | `String` | `✔`      | `N/A`              | The HTTP status code generated by the origin server for this occurrence of the problem | [Section 3.1](https://tools.ietf.org/html/rfc7807#section-3.1) |
+| **`title`**   | `String` | `✖`      | HTTP status phrase | A short, human-readable summary of the problem type                                    | [Section 3.1](https://tools.ietf.org/html/rfc7807#section-3.1) |
+| **`type`**    | `String` | `✖`      | `about:blank`      | A URI reference that identifies the problem type                                       | [Section 3.1](https://tools.ietf.org/html/rfc7807#section-3.1) |
+| **`details`** | `Object` | `✖`      | `N/A`              | additional details to attach to object                                                 | [Section 3.1](https://tools.ietf.org/html/rfc7807#section-3.2) |
 
 ``` js
 import Problem from 'api-problem'
@@ -85,7 +85,7 @@ prob.toString() //=> [403] You do not have enough credit ('https://example.com/p
 
 ### Method : `<void>` `send(response)`
 
-uses [`response.writeHead`](https://nodejs.org/docs/latest/api/http.html#http_response_writehead_statuscode_statusmessage_headers) and [`response.end`](https://nodejs.org/docs/latest/api/http.html#http_response_end_data_encoding_callback) to send an appropriate error respnse message with the `Content-Type` response header to \[`application/problem+json`\]\[spec-3\]
+uses [`response.writeHead`](https://nodejs.org/docs/latest/api/http.html#http_response_writehead_statuscode_statusmessage_headers) and [`response.end`](https://nodejs.org/docs/latest/api/http.html#http_response_end_data_encoding_callback) to send an appropriate error respnse message with the `Content-Type` response header to [`application/problem+json`](https://tools.ietf.org/html/rfc7807#section-3)
 
 ``` js
 import http from 'http'
@@ -97,7 +97,7 @@ Problem.send(response)
 
 ### Express Middleware
 
-A standard connect middleware is provided. The middleware intercepts Problem objects thrown as exceptions and serializes them appropriately in the HTTP response while setting the `Content-Type` response header to \[`application/problem+json`\]\[spec-3\]
+A standard connect middleware is provided. The middleware intercepts Problem objects thrown as exceptions and serializes them appropriately in the HTTP response while setting the `Content-Type` response header to [`application/problem+json`](https://tools.ietf.org/html/rfc7807#section-3)
 
 ``` js
 import express from 'express'
diff --git a/docs/README.md b/docs/README.md
index 01dbac9..16198f2 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -102,3 +102,7 @@ app.get('/', (req, res) => {
 
 app.use(Middleware)
 ```
+
+[spec-3]: https://tools.ietf.org/html/rfc7807#section-3
+[spec-3.1]: https://tools.ietf.org/html/rfc7807#section-3.1
+[spec-3.2]: https://tools.ietf.org/html/rfc7807#section-3.2