APA

Pitman R. L., Spear L. B. & Force M. P.Marine birds of Malpelo island, Colombia. : .

Chicago

Pitman Robert L, Spear Larry B and Force Michael P.Marine birds of Malpelo island, Colombia. : .

Harvard

Pitman R. L., Spear L. B. and Force M. P.Marine birds of Malpelo island, Colombia. : .

MLA

Pitman Robert L, Spear Larry B and Force Michael P.: . .