http://www.swmed.edu/stars/resources/alpern.ppt (http://www.swmed.edu/stars/resources/alpern.ppt)
http://www.bernardinello.it/membrane_ing.htm (http://www.bernardinello.it/membrane_ing.htm)
http://www.chemistry.ucsc.edu/smdrs/ (http://www.chemistry.ucsc.edu/smdrs/)