OAF? (Sorry, my American keyboard won't let me put the little dots above the O)
If you really want to, you can do it by writing it in WORD using Insert Symbol then copying it into your posting. There's also a clever way for the computer literate using ASCII codes
The easiest way is to Google for a list of letters with accents which you can enter simply using the ALT key plus 4 digits.
If you're running a Windoze-based computer, there's a utility program that will give you the same info. It's called
Charmap. It can be found in Start Menu | Programs | Accessories | System tools. Its operation is a little strange, but then, it's an old program.
Anyway, you can select the font you want (not absolutely necessary for special characters) and then the letter with or without diacritical marks like the umlaut (two dots, [Charmap calls it Diaeresis, which I believe to be incorrect]), accent ague (upwards-pointing accent), accent grave (downward-pointing accent) or accent circumflex (inverted 'v') and use 'em with the indicated 4-character Alt-code or select, then copy and paste.
The one I use all the time is Alt-0189 that gives me the "1/2" character: ½ that can be used for half-liter displacement: 2½ instead of 2.5 since I don't like to have dots in my filenames except for the one preceding the extension...my naming scheme could be the subject of a doctoral dissertation (which, of course, would be rejected.) Moving right along, Alt-0188 produces ¼ and Alt-0190 gives ¾. Unfortunately, there's no way to annotate tenths of a liter like 2.4, so I use the apostrophe: 2'4.
The code for a lower case o-umlaut is Alt-0246: ö and the leading zero is required. Upper case is Alt-0214: Ö
hth,
RtR