anchor.diff:          .col-lg-6
               button.btn.btn-block.btn-success(
               ng-click="documentRefSubmit(new_document)"
  -            ng-disabled="disable_button") Create reference
  +            ng-disabled="disable_button || newDocumentForm.$invalid") Create reference
           .col-lg-6
               button.btn.btn-block.btn-danger(ng-click="closeDialog()") Cancel
positive.code:                             input.form-control(
                              name="title"
                              type="text"
                              placeholder="Title (required)..."
                              ng-model="new_document.title"
                              autocomplete="off")
  
negative.code:                             placeholder="Year published (required)..."
                              ng-model="new_document.year"
                              ng-pattern="yearPattern"
                              required
                              autocomplete="off")
  
                  // EXISTING DOC
  