SA nursing journal. SA verplegingstydskrif
Freeman SD.
Science. 1972 Apr 07;176(4030):7. doi: 10.1126/science.176.4030.7-a.
PMID: 17784403
Cronin JW.
Science. 1994 Sep 23;265(5180):1791. doi: 10.1126/science.265.5180.1791-a.
PMID: 17797204
Eisenberg L.
Science. 1992 Oct 02;258(5079):16. doi: 10.1126/science.258.5079.16.
PMID: 17835879
Martini M, Paleari A, Spinolo G, Vedda A.
Phys Rev B Condens Matter. 1995 Jul 01;52(1):138-142. doi: 10.1103/physrevb.52.138.
PMID: 9979585
Burbidge G.
Science. 2008 Mar 14;319(5869):1484. doi: 10.1126/science.319.5869.1484b.
PMID: 18339922