text: var tree = Object.create(null);
  
  tree.Node = require('./node');
  tree.Alpha = require('./alpha');
  tree.Color = require('./color');
  tree.AtRule = require('./atrule');
  // Backwards compatibility
  tree.Directive = require('./directive');
  tree.DetachedRuleset = require('./detached-ruleset');
  tree.Operation = require('./operation');
  tree.Dimension = require('./dimension');
  tree.Unit = require('./unit');
  tree.Keyword = require('./keyword');
  tree.Variable = require('./variable');
  tree.Property = require('./property');
  tree.Ruleset = require('./ruleset');
  tree.Element = require('./element');
  tree.Attribute = require('./attribute');
  tree.Combinator = require('./combinator');
  tree.Selector = require('./selector');
  tree.Quoted = require('./quoted');
  tree.Expression = require('./expression');
  tree.Declaration = require('./declaration');
  // Backwards compatibility
  tree.Rule = require('./rule');
  tree.Call = require('./call');
  tree.URL = require('./url');
  tree.Import = require('./import');
  tree.mixin = {
      Call: require('./mixin-call'),
      Definition: require('./mixin-definition')
  };
  tree.Comment = require('./comment');
  tree.Anonymous = require('./anonymous');
  tree.Value = require('./value');
  tree.JavaScript = require('./javascript');
  tree.Assignment = require('./assignment');
  tree.Condition = require('./condition');
  tree.Paren = require('./paren');
  tree.Media = require('./media');
  tree.UnicodeDescriptor = require('./unicode-descriptor');
  tree.Negative = require('./negative');
  tree.Extend = require('./extend');
  tree.RulesetCall = require('./ruleset-call');
  
  module.exports = tree;
  