I am graduating this MAY and I want my parents to be here at the time. Apart from an invitation letter from my University, what else do I need to send to parents so that they can apply for the visa? Do I need to send my transcripts? Also, how early can they apply for the visa? Is there a minimum number of months/days before intended entry to the US for my parents to apply for visa? Put in another way, can they apply for a visa in december/january to come to the US in MAY?