@INBOOK {LYASSE:2001, title = {Options for increasing P availability from low creative rock phosphate}, author = {Lyasse, O. and Tossah, B. * and Vanlauwe, B. and Diels, J. and Sanginga, P. and Merckx, R. }, year = {2001}, type = {Integrated plant nutrient management in sub-Saharan Africa: from concept and practice.}, pages = {225--237}, publisher = {Wallingford, Oxon, UK: CABI}, }