Just one more question. How would I cite this as an endnote citation in a book, where you got the information regarding the assignments of batteries to the brigades in Van Dorn's Army of the West? For this one:

"Military Departments -- Letters Sent and Orders, Artillery Brigade, Army of the West, April - July 1862
Ch II, Vol 266
NARA RG 109"

I think RG 109 is the roll of microfilm it's on. What is the Chapter II, Vol. 266 part of? Thanks again for your very detailed responses Danny.