Expression of p21 protein predicts clinical outcome in DLBCL patients older than 60 years treated with R-CHOP but not CHOP: a prospective ECOG and Southwest Oncology Group correlative study on E4494., Winter, Jane N., Li Shuli, Aurora Vikas, Variakojis Daina, Nelson Beverly, Krajewska Maryla, Zhang Lijun, Habermann Thomas M., Fisher Richard I., Macon William R., et al. , Clin Cancer Res, 2010 Apr 15, Volume 16, Issue 8, p.2435-42, (2010)