1. Harrison, W.G. (1991) in “Marine Particles: Analysis and Characterization”, Geophysical Monograph 63, 33–36.
2. Fuchs, A., and van Bekkum, H. (199) Chem. Magaz., 320–321.
3. Van der Toorn, L.J. (1988) “Strategy for Biomass Conversion”, Shell brochure.
4. De Leenheer, L., and Hoebregs, H. (1992) Contribution to the 2nd Eur. Training Course, Rolduc, The Netherlands.
5. Estimates of A. Voragen (1992) 2nd European Training Course, Rolduc, The Netherlands.