rgommers/scipy — comment on commit c1a25df186bd5773bb8322ab4066b1e232204797
File:  line 0
By WarrenWeckesser:

I think the sign of the continuity correction should depend on whether U is bigger or smaller than n1*n1/2. See, for example,
http://faculty.vassar.edu/lowry/ch11a.html
or
http://www.unistat.com/guide/nonparametric-tests/unpaired-samples