Notes, Comments and Preliminary results Dec 18 2015 Jeremy Nguyen and Jen-je Su   Combining linear and nonlinear unit root tests with an application to PPP.   Abstract  Contact Information  Citation  Full Text  -  Note   Jul 30 2010 Jen-je Su , Wai-kong (adrian) Cheung and Astrophel (kim) Choo   On the power of modified Kapetanios-Snell-Shin (KSS) tests   Abstract  Contact Information  Citation  Full Text  -  Note