Zou D, An G, Zhu G, Wang J, Shi L, Meng H, Xu Y, Sui W, Deng S, Zhan F, Qiu L. Secondary monoclonal gammopathy of undetermined significance is frequently associated with high response rate and superior survival in patients with plasma cell dyscrasias. Biol Blood Marrow Transplant. 2014 Mar; 20(3):319-25.