GPS 2.1: enhanced prediction of kinase-specific phosphorylation sites with an algorithm of motif length selection. - Xue, Yu; Liu, Zexian; Cao, Jun; Ma, Qian; Gao, Xinjiao; Wang, Qingqi; Jin, Changjiang; Zhou, Yanhong; Wen, Longping; Ren, Jian (PEDS: Protein Engineering, Design & Selection, 2011)