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The 12-sided plywood farrowing house at present being produced and presented by Nutrena Mills, Inc., of U.S.A., under the name
an investigation into the winter operation of concentric portable farrowing houses under manitoba climatic conditions
Lapp, H.M. and K.W. Domier 1961. AN INVESTIGATION INTO THE WINTER OPERATION OF CONCENTRIC PORTABLE FARROWING HOUSES UNDER Manitoba CLIMATIC CONDITIONS. Canadian Agricultural Engineering 3(1):26-29.