Not much money for Science in Colombia ?
The ultra basic mathematics in the Rietveld method are available for free at the author himself Web site : http://home.wxs.nl/~rietv025/
In paperback, the book "The Rietveld Method" can be obtained for less than 10-40 euros : http://www.fetchbook.co.uk/compare.do?search=0198559127&startFrom=1
Armel
