I think, "A practical guide to modelling cognitive processes" can you help. It has been write by Maarten W. van Someren, Yvonne F. Barnard and Jacobijn A.C. Sandberg. I attach link to this book: ftp://akmc.biz/ShareSpace/ResMeth-IS-Spring2012/Zhora_el_Gauche/Reading%20Materials/Someren_et_al-The_Think_Aloud_Method.pdf