== References ==
<nocite>
BIDDLE1992
BJORN1940
BROGGER1921
BERSU1966
GRAHAM-CAMPBELL1980
GRAHAM-CAMPBELL1994
GRAHAM-CAMPBELL1998
HARRIS2011
LOVLID2009
LOVLID2010
NICOLAYSEN1882
OSTERGARD2004
OWEN1999
RICHARDS2004
ROESDAHL1992
SPEED2004
WELANDER1987
</nocite>
<biblio force=false>#[[Template:Bib]]</biblio>