http://www.englishpage.com/prepositions/prepositions.html
http://www.world-english.org/prepositions2.htm
http://www.englisch-hilfen.de/en/exercises/structures/prepositions_place_time.htm
http://web2.uvcs.uvic.ca/elc/studyzone/200/grammar/prepo.htm
http://newton.uor.edu/facultyfolder/rider/pronouns.htm