It would be nice and look a lot more professional if we stuck to one way of spelling Imperial units and I propose the spelling as shown in next page. In general this is in line with the spelling used by the Society of Petroleum Engineers (SPE) in one of their guides.The only suggestion I make is that time units are spelled the same in the SI and IMPERIAL system, thus: year is "a" and not "yr" and hour is "h" and not "hr". I know that "yr" is as clear as "a" but why have two? I can also live with "M" and "MM" for thousand and million although MM really stands for two thousand in the system where M stands for one thousand, as I (representing the old generation) am so used to it. Unfortunately m and M are also used for million. Also writing "lb" instead of "lbm" or "lbf" as the case may be does not bother me too much, as we hopefully know from the text what is meant. The ambiguous or not generally used words "billion", "trillion" and "milliard" will be difficult to get out of the spoken language but should be replaced by alternatives in written language. My advice to those that are stubborn is: "Please define what billion is!!" Then I have no problem.