• has_many
  through - Self-referential has_many :through associations
  in Ruby/Rails with bi-directional has_many self-referential through
• has_many :through: Self-referential has_many :through associations
  in Ruby/Rails with rails rubyonrails self-referential tips
• zetetic
  Social Networking with Rails using ActsAsNetwork
  in Ruby/Rails with actsasnetwork bi-directional has_many self-referential tails through

self-referential from all users