An ArgumentError occurred in citations#index:

  wrong number of arguments (given 0, expected 1)
  app/models/citation.rb:75:in 'as_json'


-------------------------------
Request:
-------------------------------

  * URL        : https://www.whatdotheyknow.com/citations.json
  * HTTP Method: GET
  * Parameters : {"controller" => "citations", "action" => "index", "format" => "json"}

-------------------------------
Backtrace:
-------------------------------

  app/models/citation.rb:75:in 'as_json'
  app/controllers/citations_controller.rb:20:in 'block (2 levels) in CitationsController#index'
  app/controllers/citations_controller.rb:18:in 'CitationsController#index'