Notes on cell counting:
http://www.ruf.rice.edu/~bioslabs/methods/microscopy/cellcounting.html
http://www.lo-laboroptik.de/englisch/info/info.html
http://books.google.no/books?id=EaLysIpGTK0C&pg=PA53&lpg=PA53&dq=Burker%27s+chamber,&source=bl&ots=9NbnJtPkv3&sig=HS3ssNs02sCEUl1OlWwcmEbI3WA&hl=no&sa=X&ei=PtnTU4X-OcmAywPco4DQCQ&ved=0CGMQ6AEwCg#v=onepage&q=Burker's%20chamber%2C&f=false