Doprava.cx
Tariffs, tourist tickets and luggage transport fees on Prague's public transport system explained.
http://www.doprava.cx/english/praha.php#tarif

DP-Praha
All you need to know about the different types of tickets available, where to buy them, ticket inspections and more.
http://www.dp-praha.cz/en/tarif_ceny.htm

DP-Praha
Click on the link marked "Tariffs and Fares", to access information about ticket inspections on Prague's public transport network.
http://www.dp-praha.cz/en/index.htm

MyCzechRepublic
Useful tips about tickets and fares on the Prague public transport network.
http://www.myczechrepublic.com/prague/tickets_fares.html

Prague Information Service
Contains a note on Prague's ticket inspectors at the bottom of the page.
http://www.pis.cz/a/prague/dopraa/dopraa.html

Praguepoint
Information on Prague's ticket inspectors and how to spot a fake one.
http://www.praguepoint.cz/Eng/rtransport.html