To come to Clark to study, work, or conduct research, you will need a visa document from the International Students and Scholars Office (ISSO). The ISSO provides a sample invitation letter template as a courtesy but cannot guarantee that your visitor will have their visa approved.The reason you're traveling to Canada determines the way you apply and the documents you need to submit with your visa application. : Each applicant must complete and sign a visa application. Each applicant shall submit a complete and signed application form individually. Submit the complete application. 3.1. Receive the application. This post contains a guide to writing your own Invitation Letter for Immigration and a sample Affidavit of Support and Guarantee for visiting relatives abroad. Want a cover letter for visa application?