Is Einstein sole proprietor of E=mc2 equation?

WASHINGTON: A little known Austrian physicist may have contributed to Einstein's famous equation E=mc, American scientists have claimed.
In a study to be published in the European Physical Journal H, Stephen Boughn from Haverford College in Pensylvannia and Tony Rothman from Princeton University in New Jersey argue how Austrian physicist Friedrich Hasenohrl's work, may have contributed to the equation E=mc.
The physicists outline the role played by Hasenohrl in establishing the proportionality between the energy (E) of a quantity of matter with its mass (m) in cavity filled with radiation.
In 1905, Einstein found the correct relationship between inertial mass and electromagnetic energy, which is E=mc.
The authors of the study believe the notion that mass and energy should be related did not originate solely with Hasenohrl. Nor did it suddenly emerge in 1905, when Einstein published his paper, as popular belief would have it.
Given the lack of recognition for Hasenohrl's contribution, the authors examined the his original work on blackbody radiation in a cavity with perfectly reflective walls.
The study seeked to identify the blackbody's mass changes when the cavity is moving relative to the observer . They then explored the reason why he arrived at an energy/mass correlation with the wrong factor, namely at the equation: E=(3/8) mc2. Hasenohrl's error, they believe, stems from failing to account for the mass lost by the blackbody while radiating.