Baseline stage, severity, and effort effects differentiate stable smokers from maintainers and relapsers.
Redding CA, Prochaska JO, Paiva A, Rossi JS, Velicer W, Blissmer BJ, Greene GW, Robbins ML, Sun X. Subst Use Misuse. 2011; 46(13):1664-74. Epub 2011 Mar 30.