1. History and development of soil testing;Anderson;Journal of Agricultural and Food Chemistry,1960
2. Fertilisation recommendations for arable crops, and horticultural crops;Anonymous;Praktijonderzoek voor de akkerbouw en vollegrondsgroenteteelt,1999
3. Anonymous 2002 Fertilisation recommendation for grassland, and forage crops. Commissie Bemesting Grasland en Voedergewassen. (In Dutch) http://www.bemestingsadvies.nl