1. Effect of cropping system on the soil organic matter content. I. Small-plot experiments with incorporation of straw and animal manure, 1956–1986 (in Danish with English summary);Christensen;Tidsskrift for Planteavl,1988
2. Effects of animal manure and mineral fertilizer on the total carbon and nitrogen contents of soil size fractions;Christensen;Biol. Fert. Soils,1988
3. Effect of cropping system on the soil organic matter content. II. Field experiments on a sandy loam, 1956–1985 (in Danish with English summary);Christensen;Tidsskrift for Planteavl,1990
4. Physical fractionation of soil and organic matter in primary particle size and density separates;Christensen;Adv. Soil Sci.,1992