diff --git a/src/ol/expression/expression.js b/src/ol/expression/expression.js
index cee19e79c3..c8f008a0b7 100644
--- a/src/ol/expression/expression.js
+++ b/src/ol/expression/expression.js
@@ -4,17 +4,15 @@ goog.provide('ol.expression.Literal');
 goog.provide('ol.expression.Not');
 
 
+
 /**
- * Support an extremely limited subset of ECMAScript 5.1
- * http://www.ecma-international.org/ecma-262/5.1/
+ * Base class for all expressions.  Instances of ol.Expression correspond to
+ * a limited set of ECMAScript 5.1 expressions.
+ * http://www.ecma-international.org/ecma-262/5.1/#sec-11
+ *
+ * This base class should not be constructed directly.  Instead, use one of
+ * the subclass constructors.
  *
- * Inspired by Esprima (https://github.com/ariya/esprima)
- * BSD Licensed
- */
-
-
-
-/**
  * @constructor
  */
 ol.expression.Expression = function() {};
diff --git a/src/ol/expression/lexer.js b/src/ol/expression/lexer.js
index 0eef619bc5..cefb950cff 100644
--- a/src/ol/expression/lexer.js
+++ b/src/ol/expression/lexer.js
@@ -1,3 +1,18 @@
+/**
+ * The logic and naming of methods here are inspired by Esprima (BSD Licensed).
+ * Esprima (http://esprima.org) includes the following copyright notices:
+ *
+ * Copyright (C) 2013 Ariya Hidayat <ariya.hidayat@gmail.com>
+ * Copyright (C) 2013 Thaddee Tyl <thaddee.tyl@gmail.com>
+ * Copyright (C) 2012 Ariya Hidayat <ariya.hidayat@gmail.com>
+ * Copyright (C) 2012 Mathias Bynens <mathias@qiwi.be>
+ * Copyright (C) 2012 Joost-Wim Boekesteijn <joost-wim@boekesteijn.nl>
+ * Copyright (C) 2012 Kris Kowal <kris.kowal@cixar.com>
+ * Copyright (C) 2012 Yusuke Suzuki <utatane.tea@gmail.com>
+ * Copyright (C) 2012 Arpad Borsos <arpad.borsos@googlemail.com>
+ * Copyright (C) 2011 Ariya Hidayat <ariya.hidayat@gmail.com>
+ */
+
 goog.provide('ol.expression.Lexer');
 goog.provide('ol.expression.Token');
 goog.provide('ol.expression.TokenType');
@@ -79,7 +94,8 @@ ol.expression.Token;
 
 
 /**
- * Lexer constructor.
+ * Lexer constructor.  Provides a tokenizer for a limited subset of ECMAScript
+ * 5.1 expressions (http://www.ecma-international.org/ecma-262/5.1/#sec-11).
  *
  * @constructor
  * @param {string} source Source code.
@@ -226,9 +242,10 @@ ol.expression.Lexer.prototype.isIdentifierStart_ = function(code) {
 /**
  * Determine if the given identifier is an ECMAScript keyword.  These cannot
  * be used as identifiers in programs.  There is no real reason these could not
- * be used in ol expressions - so it might be worth allowing them.
+ * be used in ol expressions - but they are reserved for future use.
  *
  * http://www.ecma-international.org/ecma-262/5.1/#sec-7.6.1.1
+ *
  * @param  {string} id Identifier.
  * @return {boolean} The identifier is a keyword.
  * @private
diff --git a/src/ol/expression/parser.js b/src/ol/expression/parser.js
index 33de610eb0..ceb53d7f21 100644
--- a/src/ol/expression/parser.js
+++ b/src/ol/expression/parser.js
@@ -1,3 +1,18 @@
+/**
+ * The logic and naming of methods here are inspired by Esprima (BSD Licensed).
+ * Esprima (http://esprima.org) includes the following copyright notices:
+ *
+ * Copyright (C) 2013 Ariya Hidayat <ariya.hidayat@gmail.com>
+ * Copyright (C) 2013 Thaddee Tyl <thaddee.tyl@gmail.com>
+ * Copyright (C) 2012 Ariya Hidayat <ariya.hidayat@gmail.com>
+ * Copyright (C) 2012 Mathias Bynens <mathias@qiwi.be>
+ * Copyright (C) 2012 Joost-Wim Boekesteijn <joost-wim@boekesteijn.nl>
+ * Copyright (C) 2012 Kris Kowal <kris.kowal@cixar.com>
+ * Copyright (C) 2012 Yusuke Suzuki <utatane.tea@gmail.com>
+ * Copyright (C) 2012 Arpad Borsos <arpad.borsos@googlemail.com>
+ * Copyright (C) 2011 Ariya Hidayat <ariya.hidayat@gmail.com>
+ */
+
 goog.provide('ol.expression.Parser');
 
 goog.require('goog.asserts');