Invitation Letter & Visa If you need an official invitation letter for the purposes of a visa to the United States, please allow sufficient time to process and mail the letter. We recommend to contact us with your invitation request at least 60 days prior (by June 8, 2017) to the conference date (and as soon as you complete registration). Please note that your request can be accepted and a letter sent by the Organizing Committee only if you have completed the registration process. Thank you for your understanding in this matter. Information about travel (and visa requirements) to the USA can be found below: https://travel.state.gov/content/visas/en/forms.html https://travel.state.gov/content/visas/en/visit/visa-waiver-program.html