"Interaction picture" . "Dirac picture" . . "Interaction_picture#Schwinger-Tomonaga_equation" . "interaction Hamiltonian" . "interaction (Dirac) picture" . . . ":Interaction picture#Schwinger-Tomonaga equation" . "interaction picture" . "Interaction picture" . "interaction or Dirac picture" . . . "Tomonaga\u2013Schwinger equation" . . . . .