(Kohlbrecher, Eisermann et al. 1992; Boyd, Cvitkovitch et al. 1994)
From 2006.igem.org
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=8132321
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=1551842