We are frequently asked how to cite SmartPLS, especially in academic publications, as it is required by the license agreement.
SmartPLS 3 (see http://www.smartpls.de/faq#q12):
Ringle, Christian M./ Wende, Sven/ Becker, Jan-Michael (2015): Smartpls 3. Bönningstedt: SmartPLS. Retrieved from http://www.smartpls.com.
SmartPLS 2:
Ringle, Christian M./ Wende, Sven/ Will, Alexander (2005): SmartPLS 2. Hamburg: SmartPLS. Retrieved from http://www.smartpls.com.