Quite frequently mathematical formulæ in reports, theses or even articles are not written correctly. Indeed, the basic rules for composing the formulæ are almost never explicitly stated. This article provides some suggestions to fill this gap.
http://www.tug.org/TUGboat/Articles/tb29-2/tb92guiggiani.pdf (English)
http://www.guit.sssup.it/download/ (Italian)
some notes by Albert Einstein (photo by monica, Paris, Cité des Sciences)