Ancestry has the 1935 phone directory of Magdeburg
https://www.ancestry.ca/search/collections/30295/
genealogy.net has the 1930 and 1938 directories
http://wiki-de.genealogy.net/Magdeburg/Adressbuch_1938
http://wiki-de.genealogy.net/Magdeburg/Adressbuch_1932
these are all scans, no indexing has been done, so you have to browse through the pages and be able to read black letters. 
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Andrea Schwab, Montreal, Canada