Calculus in 1969

Integral Operators in the Theory of Linear Partial Differential Equations by Bergman, Stefan

Integral Operators in the Theory of Linear Partial Differential Equations by Bergman, Stefan

Real and Abstract Analysis by Hewitt, Edwin, Stromberg, Karl

Linear Partial Differential Operators by Hörmander, Lars

Generalized Feynman Amplitudes by Speer, Eugene R.