ACKNOWLEDGEMENTS

For the compilation of these Guidelines the author has drawn extensively on the information, experience and (sometimes confidential) documents of colleagues in other institutes who, in one way or another, are engaged in setting up or maintaining and improving quality assurance systems, mostly in the framework of laboratory accreditation. The author wishes to express his gratitude to all those who have contributed to his documentation and (re)forming his ideas in any way, particularly the following persons:

Messrs. F.T. Blank and K. Roelse	Laboratory for Soil and Crop Testing (BLGG), Oosterbeek.
Dr. V.J.G. Houba	Dept. of Soil Science and Plant Nutrition, Wageningen Agricultural University, Wageningen.
Mr. M. Moura	Delft Geotechnics, Delft.
Dr. B.C van Schijndel	Quality and Logistics Project, Post Tertiary Education Dept., Hogeschool Utrecht, Utrecht.
Dr. J.J.T.W.A. Strik	National Institute of Public Health and Environmental Protection (RIVM), Bilthoven.
Ms. G. Tielens	Institute for Inland Water Management and Waste Water Treatment (RIZA), Lelystad.
Messrs. J. Vuik and J. Warbout	IWACO Environmental Laboratory, Rotterdam.
Mr. Th. C. Wolters	Environmental Laboratory, Winand Staring Centre for Integrated Land, Soil and Water Research (SC-DLO), Wageningen.(All of the Netherlands)

Thanks are also due to staff of the ISRIC laboratory (Messrs. J. Huting, N. Manuchehri, A.J.M. van Oestrum, R.A. Smaal) for their cooperation and contributions, and to Mr. W.C.W.A. Bomer for his assistance with the drawings. Dr. E.M. Bridges kindly removed most of the grammatical errors.

The author is particularly grateful to Dr. C.S. Ofori, formerly of the Food and Agriculture Organization of the United Nations (FAO), Rome, and to Dr. J.L. Pleysier, formerly of the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, for their encouragement to undertake the compilation of these Guidelines.