Karl Gauss (1777-1855) discusses the meaning of integrals with complex limits and briefly examines the dependence of such integrals on the chosen path of integration.
Citation:
Editors. "Gausss work on integrals".
The Literary Encyclopedia. First published 01 May 2009
[http://www.litencyc.com/php/stopics.php?rec=true&UID=6239, accessed 20 June 2013.]