Annual Reports, Secretary of Agriculture, 1917 and 1918.
Farmers' Bulletins Nos. 594, 688, 703, 922, 930 and others
relating to marketing by parcel-post.
FIELD, ARTHUR S.--Rates and Practises of Express Companies; and The
Express Charges Prescribed by the Interstate Commerce Commission,
American Economic Review, 1913, volume 3, pages 314 and 831.