[1] Crawley P, Jónsson B.Refinements for infinite direct decompositions of algebra systems[J].Pacific J Math, 1964, 14(3):797-855.
[2] Warfield R B. Exchange rings and decompositions of modules[J].Math Ann, 1972, 199(1):31-36.
[3] Ara P.Extensions of exchange rings[J].J Algebra, 1997, 197(2):409-423.
[4] Nicholson W K, Zhou Y.Clean general rings[J].J Algebra, 2005, 291(1):297-311.
[5] Zhang Hongbo.On cancellations property[D].Nanjing:Department of Mathematics of Nanjing University, 2004.(in Chinese)
[6] Dinesh Khurana, Lam T Y.Rings with internal cancellation[J]. J Algebra, 2005, 284(1):203-235.
[7] Hong C Y, Kim N K, Lee Y.Exchange rings and their extensions[J].Pure Appl Algebra, 2003, 179(1):117-126.