I'm editing a school textbook and have suddenly discovered at the 11th hour that there is a difference between the U.S. cup (236ml), the Canadian cup (227ml) and the British cup (284ml) as well as conflicting results (such as Wiki) that define them differently again - U.S.=250ml, Canadian=240ml. Apparently, the cup is derived from the more basic unit of fluid ounces, and that's not standard either. I need to find an online soruce that can authoritatively define these differences for the various units of cups, ounces, quarts and gallons. And I need to have it by - like - tomorrow morning. Help!