Batjes, N. H. A global data set of soil pH properties / N.H. Batjes. - Wageningen, The Netherlands : International Soil Reference and Information Centre, 1995. - iv, 28 p. : maps. - ISRIC technical paper ; 27 . ISBN: 9066720603 ISSN: 090233792 Subjects--Topical Terms: Soil acidity--Data processing.Hydrogen-ion concerntration--Data processing.