APA (7th ed.) Citation

Petrus Kardinal, H. Letters. Catholic Univ. of America Press.

Chicago Style (17th ed.) Citation

Petrus Kardinal, Heiliger. Letters. Washington, D.C: Catholic Univ. of America Press.

MLA (9th ed.) Citation

Petrus Kardinal, Heiliger. Letters. Catholic Univ. of America Press.

Warning: These citations may not always be 100% accurate.