1. The evidence for wormholes in deep bed filters;Baumann,1987
2. Deep bed filtration mechanisms observed with fibre optic endoscopes and CCTV;Clough,1986
3. Detachment of deposits from sand grains;Fitzpatrick,1988
4. Continuous countercurrent filtration;Fourie,1982
5. Recent results on particle deposition in sand filters;Gimbel,1978