In the NASM documentation, Instruction List:
http://www.nasm.us/doc/nasmdocb.htmlthe third column contains as stated "...and, when appropriate, one or more usage flags"
But these flags have no legend. Many of them are obvious, but some not very. What is NOLONG, UNDOC, ND, SW, AR0, SZ and many others? I suggest to add the legend to the first paragraph of this section.