Refer to "13. Reference Files and URL References for Models and Instances"
     for details on how to add, delete, and refer to reference files in Instance,
     and to add, delete, and refer to reference URLs.

　 1. Lclass reference files and reference URLs

        Select the Lclass to add, delete, reference files, add, delete,
       and reference by reference and reference URL.
  　

　 2. Sclass reference files and reference URLs

        Select the Sclass to add, delete, reference files, add, delete,
       and reference by reference and reference URL.