In EWD1308-5, EwDijkstra says:

	 :	J.A. Zonneveld and I combatted the writing errors by coding together, each with his own text in front of him; when we were done, both our texts were punched independently, the two tapes were compared mechanically and about two dozen discrepancies - if I remember correctly - showed up. The thinking errors we had tried to prevent by convincing each other why the proposed section would work.

http://www.cs.utexas.edu/users/EWD/ewd13xx/EWD1308.PDF

The keen-eyed will also see that EwDijkstra invented SimplestThing,
OnceAndOnlyOnce, YouArentGonnaNeedIt, and WorstThingsFirst.