@phdthesis{ Solr-1083722212, title = {A descriptive analysis of the extent of commercial paching in the United States}, author = {Farnsworth, Carl L.}, address = {Ann Arbor, Mich.}, publisher = {Univ. Microfilms Internat.}, year = {1984}, school = {Zugl.: Sam Houston State Univ., Diss., 1980}, }