9Farrish K W, Doolittle J A, Gamble E E, et al.Loamy substrate and forest productivity of sandy glacial drift soils in Michigan [J]. Canadian Journal of Soil Science, 1990, 70: 181-187.
10Boll J, van Rijn R P G, Weiler K W, et al. Using ground-penetrating radar to detect layers in a sandy field soil[J]. Geoderma, 1996, 70:. 117-132.