Other possible normalizations are quite idiosyncratic and particular to English. For instance, you might wish to equate ne'er and never or the British spelling colour and the American spelling color. Dates, times and similar items come in multiple formats, presenting additional challenges. You might wish to collapse together 3/12/91 and Mar. 12, 1991. However, correct processing here is complicated by the fact that in the U.S., 3/12/91 is Mar. 12, 1991, whereas in Europe it is 3 Dec 1991.