, ▁and ▁( b ) ▁understand ▁the ▁connection ▁of ▁Mass - energy ▁equivalence ▁with ▁the ▁relativ ity ▁principle . ▁ ▁Early ▁reception ▁ ▁First ▁assess ments ▁Walter ▁Kauf mann ▁( 1 9 0 5 , ▁ 1 9 0 6 ) ▁was ▁probably ▁the ▁first ▁who ▁referred ▁to ▁Ein stein ' s ▁work . ▁He ▁compared ▁the ▁theories ▁of ▁Lor ent z ▁and ▁Ein stein ▁and , ▁although ▁he ▁said ▁Ein stein ' s ▁method ▁is ▁to ▁be ▁preferred , ▁he ▁argued ▁that ▁both ▁theories ▁are ▁observation ally ▁equivalent . ▁Therefore , ▁he ▁spoke ▁of ▁the ▁relativ ity ▁principle ▁as ▁the ▁" L or ent z - E in stein ian " ▁basic ▁assumption . ▁Short ly ▁afterwards , ▁Max ▁Plan ck ▁( 1 9 0 6 a ) ▁was ▁the ▁first ▁who ▁public ly ▁def ended ▁the ▁theory ▁and ▁interested ▁his ▁students , ▁Max ▁von ▁La ue ▁and ▁Kur d ▁von ▁Mos en ge il , ▁in ▁this ▁form ulation . ▁He ▁described ▁Ein stein ' s ▁theory ▁as ▁a ▁" general ization " ▁of ▁Lor ent z ' s ▁theory ▁and , ▁to ▁this ▁" L or ent z - E in stein - The ory ", ▁he ▁gave ▁the ▁name ▁" relative ▁theory "; ▁while ▁Alfred ▁Buch erer ▁changed ▁Plan ck ' s ▁nom en cl ature ▁into ▁the ▁now ▁common ▁" theory ▁of ▁relativ ity " ▁(" E in stein sche ▁Rel ativ ität st he orie "). ▁On ▁the ▁other ▁hand , ▁Ein stein ▁himself ▁and ▁many ▁others