1. Originally published in German, Das System der Wissenschaften nach Gegenständen und Methoden was published by Vandenhoeck & Ruprecht © 1923.
2. Das System der Wissenschaften nach Gegenständen und Methoden, was reprinted in the first volume of Tillich's Gesammelte Werke** **(Stuttgart: Evangelisches Verlagswerk, 1959).
3. Das System der Wissenschaften nach Gegenständen und Methoden is currently available from De Gruyter Academic Publishers. It is included in a multiple volume publication entitled Hauptwerke (Main Works). Volume 1 / Band 1 Philosophical Writings / Philosophische Schriften includes the publication we are focused on. It is possible to buy (for a somewhat reasonable price) a .pdf of this publication from this link.
4. The System of Sciences According to Objects and Methods is the English translation of the original work. The English edition was translated by Paul Wiebe and published by Bucknell University Press © University Presses of America 1981. The title is no longer available. More information will appear if new purchase information is obtained.
5. The Complete Works of Paul Tillich is a work in development. New information will be provided here as it becomes available.