Hello, you inserted a <ref> tag in NP-complete, but none of the Harvard references you listed matches anything in the “References” section. You have to include full bibliographic details, otherwise there is no way for anyone else to know what is “Bern (1990)” supposed to refer to.—Emil J. 12:00, 28 February 2013 (UTC)
- Excuse me, already fixed.Sombra Corp. (talk) 13:45, 28 February 2013 (UTC)
- Perfect, thank you.—Emil J. 14:26, 28 February 2013 (UTC)