Necessary travel visa for Hong Kong?

I am booking travel for a professor to Hong Kong, and I was wondering what type of visa he would need. He is going to be in Hong Kong for 11 days for a lecture and research. Does he need a visa for a trip this short? I know that residents of the USA, Europe, Australia, and New Zealand don't need a visa if they visit for less than 90 days in Hong Kong. But since he is there for lecture/research, does he need a business visa (F visa)? Thanks!