http://www.specialeducationguide.com

www.rnid.org.uk (hearing check)

kidshealth.org/hearing_impairment.html

www.merck.com/mmhe (online medical library)

http://en.wikipedia.org/wiki/Hearing_impairment

http://deafness.about.com/

http://study.com/academy/lesson/what-is-hearing-impairment-definition-causes-treatment.html