We are Americans who live and work in the Philippines. We wish visit Beijing for two days then board a Princess Cruise ship. We will also be visitng two other ports in China. When we apply for the Visa, is it necessary for an invitation letter, or is the receipt for payment and itinerary from the Cruise ship company enough? Also, the cruise will end in Singapore so we don't need a round trip airline ticket. Can you tell me the best way to deal with these issues? Thank you!