The biographies make for fascinating reading, though they should be read with the following warning. Zylbercweig's book is well-known for its inaccuracies, reflecting the difficult circumstances with which it was written. The Yivo Encyclopedia page on Zylbercweig has the following caveat about the book:
Zylbercweig’s encyclopedia, a monument to his extraordinary dedication, reflects both his scholarly limitations and the difficult conditions of his work. The volumes have been insufficiently edited and contain errors and imprecise data. Even more problematic is the matter of sources. Although he provides bibliographies of varying degrees of accuracy at the end of each article, much of Zylbercweig’s information is based on his subjects’ personal communications, often about their own careers. The longer articles typically consist of lengthy citations from insufficiently identified sources that can be traced, if at all, only with great effort. However, the Leksikon is also a vast source of social and cultural documentation.
Michael C. Steinlauf, writting for the Yivo Encyclopedia of Jews in Eastern Europe - link.
Bearing that in mind, I here reproduce both biographies in their English translation, with a few of my own notes afterwards.