Information was obtained from the address http://davidpratt.info/cropcirc1.htm, and the following, loosely translated and supplemented by information obtained through search engines.
Impormasyon ay nakuha mula sa address http://davidpratt.info/cropcirc1.htm, at volgende, maluwag isinalin at pupunan sa pamamagitan ng impormasyon na nakuha sa pamamagitan ng mga search engine.