By 1930 Einstein had already considered the Einstein -- Maxwell -- Dirac System ( Dongen ) .
These and other models of electromagnetism and gravity were pursued by Albert Einstein in his attempts at a classical unified field theory .
By 1930 Albert Einstein had already considered the Einstein -- Maxwell -- Dirac System ( Dongen ) .
These and other models of electromagnetism and gravity were pursued by Albert Einstein in his attempts at a classical unified field theory .