Dokuchaev, V.V., 1899. Report to the Transcaucasian Statistical Committee on Soil Taxonomy in General and Especially for the Transcaucasia. Horizontal and Vertical Soil Zones. Office Press of the Civilian Affairs Commander-in-Chief in the Caucasus, Tiflis, 19 p. (in Russian). pdf
Zakharov, S.A., 1927. A Course of Soil Science. Gosizdat, Moscow, 440 p. (in Russian). pdf
Zakharov, S.A., 1931. A Course of Soil Science, 2nd rev. ext. ed. Selkolhozgiz, Moscow, 550 p. (in Russian). pdf
Forbes, J.D., 1846. Account of experiments on the temperature of the earth at different depths, and in different soils, near Edinburgh. Transactions of the Royal Society of Edinburgh 16, 189-236. pdf
Bernard A. Keen and William B. Haines (1925) Studies in Soil Cultivation I, The evolution of a reliable dynamometer technique for use in soil cultivation experiments. Journal of Agricultural Science, 15: 375-386. pdf
William B. Haines and Bernard A. Keen (1925) Studies in Soil Cultivation II. Test of soil uniformity by means of dynamometer and plough. Journal of Agricultural Science, 15: 387-394. pdf
William B. Haines and Bernard A. Keen (1925) Studies in Soil Cultivation III. Measurements on the Rothamsted classical plots by means of dynamometer and plough. Journal of Agricultural Science, 15: 395-406. pdf
William B. Haines and Bernard A. Keen (1928) Studies in Soil Cultivation IV. A New form of traction dynamometer. Journal of Agricultural Science, 18: 724-733. pdf
W.J. Youden and A. Mehlich, Selection of efficient methods for soil sampling, Contributions of the Boyce Thompson Institute for Plant Research 9 (1937), pp. 59–70. pdf
De Gruijter, J.J., McBratney, A.B., 1988. A modified fuzzy k means for predictive classification. In: Bock,H.H.(ed) Classification and Related Methods of Data Analysis. pp. 97-104. pdf
Ohashi. Y. Fuzzy clustering and robust estimation. Presentation at the 9th meeting SAS User’s Group International. Hollywood Beach. Florida. 18-21 March 1984. pdf
Triantafilis, J. 1990. Application of Continuous Methods of Soil Classification in The Lower Namoi Valley. BSc Agr Thesis, The University of Sydney. pdf (3 MB). One of the first application of numerical taxonomy and digital soil mapping.
Legros, J.P, Benneric, P.H., 1979. MODELISATION INFORMATIQUE DE LA REPARTITION DES SOLS DANS LE PARC NATUREL REGIONAL DU PILAT. Annales de l’Universite de Savoie. Tome 4 – 1979 – Sciences Naturelles p. 63 – 68. pdf The earliest digital soil mapping.
Pollack, H.N., 1969. A Numerical Model of Grand canyon. Four Corners Geological Society Guidebook 61. pdf. An early mechanistic landscape model.