Johnston, P., Stringer, R., Santillo, D. & Howard, V. (1998). Hazard, exposure and ecological risk assessment. In Environmental Management in Practice, Volume 1: Instruments for environmental management. B. Nath, L. Hens, P. Compton & D. Devuyst [Eds]. Publ. Routledge, London. ISBN 0-415-14906-1: pp. 169-187.