1. E. Koski, and A. John “How Concrete Block Are Made” (Masonry Construction, October 1992) pp. 374–377.
2. Information on http://www.madehow.com/Volume-3/Concrete-Block.html
3. Information on http://ledrrecycling.com/benefits-green-construction-recycling/
4. Information on http://www.worldwatch.org/node/3915
5. BS. 882/1992. “British standard institute, aggregate from natural sources for concrete”