title: the diffence between references_many and has_many in mongoid
body: <p>I am new to mongoid. i start doing mongoid with rubyonrails with help of screen cast #238 of Ryan bate.</p>
  
  <p>I found in the section of "Reference" of mongoid official website describing about the has_many.</p>
  
  <p>Can anyone help me to explain what is the difference between has_many and references_many and which version of mongoid support them.</p>
  
  <p>Thanks you very much.</p>