1. Addition of fly ash in stabilized courses (in Dutch);Penning;Report DWW (Road and Hydraulic Engineering Division), MAO-R-88031,1988
2. Fly ash in mortars and concrete. Pozzolanic activity and durability, Part I and II;Fraay,1988
3. Fly ash as a Pozzolan in Concrete;Fraay;PhD thesis,1990
4. The reactivity of fly ash in concrete. A critical examination;Fraay;Cement and Concrete Research,1989
5. The use of fly ash produced from the combustion of powdered coal as a stabilization material;Fraay,1989