One Space Or Two Spaces?
http://pthree.org/2008/12/07/one-space-or-two-spaces/

Toponce, Aaron
Aaron Toponce
2008

Abstract:

When I began writing technical documentation and courseware for Guru Labs, I asked a question during training about whether we should be putting two spaces after a period, colon, question mark and exclamation point, or one. The answer shocked me, as I was hoping for the standard answer as a means of teaching the rest of my colleagues. The answer was ONE space, not two. Then, I listened to the argument.