Sleep,
                     sleepiness and
                     yawning,
                     Piero
                     Salzarulo, Samir Aboudan, Fiorenza Giganti
                     
                     
                     The
                     interplay between yawning and vigilance: a
                     review of experimental
                     evidence,
                     Adrian G. Guggisberg, Christian W.
                     Hess
                     
                     Yawning
                     across the life
                     span,
                     Fiorenza Giganti
                     
                     
                     
                     
                     
                     
                     
                     Ethologie
                     : les vertébrés supérieurs
                     non humains,
                     Bertrand Deputte 
                     
                     Ethology
                     : human
                     primates,
                     Wolter Seuntjens 
                     
                     Yawning:
                     A comparative-developmental
                     perspective,
                     James
                     R. Anderson
                     
                     
                     
                     
                     
                     
                     
                     Yawning
                     and
                     thermoregulation,
                     Andrew C. Gallup, Gordon G. Gallup
                     Jr
                     
                     
                     
                     
                     
                     
                     
                     Dopamine
                     Agonist-Induced Yawning in Rats: A Dopamine D3
                     Receptor Mediated
                     Behavior, Gregory
                     T Collins
                     
                      Pharmacology
                     -
                     Physiology,
                     Alejandro Moyaho, José Eguibar
                     
                     
                     
                     
                     
                     
                     
                     
                     Contagious
                     yawning and the
                     brain,
                     Steven M Plate
                     
                     Contagious
                     yawning and the frontal lobe: An fMRI
                     study,
                     Fatta B. Nahabk
                     
                     Do
                     chimpanzees yawn contagiously
                     ?
                     Matthew Campbell , Frans de Waal
                     
                     Lack
                     of contagious yawning in
                     autism,
                     Atsushi Senju 
                     
                     Dogs
                     catch human yawns,
                     
                     Atsushi Senju