I do not know the date of reference. what do i put in the brakets after the name

Question:

I do not know the date of reference. what do i put in the brakets after the name?

Best Answer - Chosen by Asker:

If you have any idea of at least what century, you could put for example - (poss.C16th). Otherwise just use the first known date of the reference, or your source for the information, and credit the person who used it e.g. (Charlie Burton, dictionary of wolves,1775)