Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
show (v.)
The past tense is showed, the past participle either shown or showed. (Spellings shew, shewed, and shewn are now archaic.) Edited English doesn’t use show in the sense of “appear,” as in He didn’t show for the meeting, but that sense is widely and acceptably used at all Standard Conversational levels and in Informal writing. See also SHOW UP.
