It makes no difference if you use small letters or capital letters.
Punctuation is ignored.
You do not have to include periods, decimals, commas etc. Computers reliability Spelling is important. If unsure of spelling, type as much of the correct word as possible. For example, to search for cholesterol if unable to spell it, type as much as is known. If there is more than 1 match, a list of matching subject headings will display.