Günter Hellwig

On the Necessity of Classification Into Types

Günter Hellwig, G. Hellwig, 1964 .

Partial differential equations : an introduction

Günter Hellwig, 1964 .

Elliptic Systems of Differential Equations

Günter Hellwig, G. Hellwig, 1964 .

Systems of Differential Equations of the First Order

Günter Hellwig, G. Hellwig, 1964 .