9Beuss S A, Buhler D D, Gunsolus J L. Effects of soil depth and aggregate size on weed seed distribution and viability in a silt loam soil[J]. Applied Soil Ecology, 2001, (16) :209 ~ 217.
10Syed Shahid Shaukat, Imran Ali Siddiqui. Spatial pattern analysis of seeds of an arable soil seed bank and its relationship with aboveground vegetation in an arid region [J]. Journal of Arid Environments,2003:1 ~ 17.