Cant get the association to work so I can count number of revisions per document

gistfile1.rb

Model pdm_documents:
class PdmDocument < ActiveRecord::Base
	
	has_many :revisions
End

Model pdm_revisions:
class PdmRevision < ActiveRecord::Base

	belongs_to :document


end

Controller pdm_documents_controller
class PdmDocumentsController < ApplicationController
	
	def index
		@project = Project.find(params[:project_id])
		@documents = PdmDocument.find(:all)
	end
	

View index:
			<% if not  @documents.nil? %>
			 	<% @documents.each do |document| %>
				  <tr <%= cycle("odd", "even") %>">
					<td><%= link_to(image_tag('document.png'), {:action => 'download', :id => document}) %></td>
				   	<td><%= document.time_stamp %></td>
					<td><%= link_to document.name, { :controller => "pdm_revisions", :action => "index" , :id => document, :project_id => @project }%></td>
					<td><%= document.last_revision_by %></td>
					<td><%= document.revisions.count %></td>
				  </tr>
				<% end %>
			<% end %>