Oppenheimer and Volkoff discounted the influence of heat, stating in reference to work by Landau (1932), 'even [at] 10 degrees... the pressure is determined essentially by the density only and not by the temperature' – yet it has been estimated that temperatures can reach up to approximately >10 K during formation of a neutron star, mergers and binary accretion. Another source of heat and therefore collapse-resisting pressure in neutron stars is 'viscous friction in the presence of differential rotation.'