Yazar
Douglas Helms
13 cilt bulundu.
Douglas Helms · Iowa State Press
318 sayfa · 2002
Soil surveys / United States / United States. Division of Soils / Soil scientists / History
Douglas Helms · U.S. Dept. of Agriculture, Soil Conservation Service, Economics and Social Sciences Division, NHQ
197 sayfa · 1994
United States / Officials and employees / United States. Soil Conservation Service / Soil conservation / Interviews
Douglas Helms · U.S. Dept. of Agriculture, Soil Conservation Service, Economics and Social Sciences Division, NHQ
174 sayfa · 1992
History / Soil conservation / United States / United States. Soil Conservation Service
Douglas Rees, Rhonda Helms, Catherine Haines, Alex Kahler, Carol Wolf, Mark London Williams, Anna-Marie McLemore, Lynda K. Scott, H. Scott Beazley, Linda Wisdom · Ambush Books
294 sayfa · 2012
Kategori yok
Douglas Helms · U.S. Dept. of Agriculture, Natural Resources Conservation Service
306 sayfa · 2008
United States / Forecasting / Water-supply / Snow surveys / Officials and employees
Douglas Helms · Lulu.com
733 sayfa · 2012
Boll weevil / Soils / Soil conservation / Water conservation / Biography
Douglas Helms, Douglas E. Bowers · Agricultural History Society
367 sayfa · 1993
Agricultural systems / Sustainable agriculture / Congresses / Agriculture / Agricultural ecology
Douglas Helms, Susan Flader · Agricultural History Society
244 sayfa · 1985
United States / Soil conservation / United States. Soil Conservation Service / Congresses / History
Douglas Helms, Anne B. W. Effland, Patricia J. Durana · Wiley & Sons, Limited, John
331 sayfa · 2008
Soil science / Soil surveys
Robert M Bray, Douglas L. Fountain, Barbara J. York, Rick L Williams, Robert F. Helms, Defense Manpower Data Center (U. S.) · Yayınevi bilinmiyor
Sayfa sayısı yok
Kategori yok
Robert M Bray, Thomas R Curtin, Barbara J York, Rick L Williams, Robert F Helms, Douglas L Fountain, Defense Manpower Data Center (U. S.) · Yayınevi bilinmiyor
Sayfa sayısı yok
Kategori yok