Rails 3 association with order by field with belongs to relation

rubyonrails-talk
1

Hi,     I have three model subject, document_types and document.

    class Subject < AR          has_many :documents     end

    class DocumenType < AR         has_many :documents     end

    class Document < AR        belongs_to :subject        belongs_to :document_types     end

    I need to list all the documents under a subject order by document_type's start_date.     What is exact syntax I will use in this association to solve this problem.

Thanks in advance.