. . "Quantum mechanics" . . . . . . . . . "Online-Publikation" . . . . . . . . . . . . . . . . . . "The Schwinger action principle and effective action"@en . "The Schwinger action principle and effective action" . . . . . . "The Schwinger Action Principle and Effective Action" . "The Schwinger Action Principle and Effective Action"@en . "Quantenfeldtheorie." . . "Schwinger-Modell." . . "Quantum physics" . .