http://www.nonstopenglish.com/exercise.asp?exid=400
http://www.tcet.com/eaonline/GrammarCentral/thereis.html
http://www.members.iinet.net.au/~adelegc/grammar/there_is/thereis.html
http://www.english-room.com/read_6a.htm
http://english.baladre.org/sedaviwebfront/thereisare.htm
http://www.inglesmundial.com/I7/grammar.htm
http://www.tcet.com/eaonline/GrammarCentral/thereis.html
http://www.members.iinet.net.au/~adelegc/grammar/there_is/thereis.html
http://www.english-room.com/read_6a.htm
http://english.baladre.org/sedaviwebfront/thereisare.htm
http://www.inglesmundial.com/I7/grammar.htm