<%= search_form_for @q, url: collection_path do |f| %>

  <%= f.label :id_eq, 'ID igual a' %>
  <%= f.text_field :id_eq %>
  <%= f.label :numero_eq %>
  <%= f.text_field :numero_eq %>
  <%= f.label :autor_eq %>
  <%= f.text_field :autor_eq %>
  <% #TODO: Add tags to this form with the javascript part %>
  <%= f.label :tags_id_eq, 'Tags' %>
  <%= f.select(:tags_id_eq, Tag.all.map { |t| [t.name, t.id] }, {:multiple => true}, {:class  => 'chzn-select'}) %>
  <%= f.label :pases_descripcion_cont %>
  <%= f.text_field :pases_descripcion_cont %>
  <%= f.label :primer_pase_area_name_cont %>
  <%= f.text_field :primer_pase_area_name_cont %>
  <%= f.label :ultimo_pase_area_name_cont %>
  <%= f.text_field :ultimo_pase_area_name_cont %>

  <%= f.label :pases_ingreso_gteq, 'Ingresada entre:'%>
  <%= f.text_field :pases_ingreso_gteq, :class => 'datepicker' %>
  <%= f.label :pases_ingreso_lteq, 'y' %>
  <%= f.text_field :pases_ingreso_lteq, :class => 'datepicker' %>

  <%= f.submit %>
<% end %>

<%= search_form_for @q, url: collection_path do |f| %>

  <%= f.label :id_eq, 'ID igual a' %>
  <%= f.text_field :id_eq %>
  <%= f.label :numero_eq %>
  <%= f.text_field :numero_eq %>
  <%= f.label :autor_eq %>
  <%= f.text_field :autor_eq %>
  <% #TODO: Add tags to this form with the javascript part %>
  <%= f.label :tags_id_eq, 'Tags' %>
  <%= f.select :tags_id_in, options_from_collection_for_select(Tag.all, :id, :name),
      {}, class: 'chzn-select', multiple: true %>
  <%= f.label :pases_descripcion_cont %>
  <%= f.text_field :pases_descripcion_cont %>
  <%= f.label :primer_pase_area_name_cont %>
  <%= f.text_field :primer_pase_area_name_cont %>
  <%= f.label :ultimo_pase_area_name_cont %>
  <%= f.text_field :ultimo_pase_area_name_cont %>

  <%= f.label :pases_ingreso_gteq, 'Ingresada entre:'%>
  <%= f.text_field :pases_ingreso_gteq, :class => 'datepicker' %>
  <%= f.label :pases_ingreso_lteq, 'y' %>
  <%= f.text_field :pases_ingreso_lteq, :class => 'datepicker' %>

  <%= f.submit %>
<% end %>

Fix select for collection on search.
Fix select for collection on search.