http://www.thc.state.tx.us/markerdesigs/madnrcrit.html
http://www.thc.state.tx.us/markerdesigs/madmark.html
http://www.tshaonline.org/handbook/online/articles/MM/qfm1_print.html
http://www.tshaonline.org/handbook/online/articles/ZZ/fza3.html
http://www.tshaonline.org/handbook/online/articles/RR/ngr1.html