I am writing an abstract of When Money Was In Fashion: Henry Goldman, Goldman Sachs, and the Founding of Wall Street by June Breton Fisher for my next readers' advisory book. In these abstracts of biographical books, I include birth and death years in parentheses by the subjects' names in the abstracts. Because Fisher never actually states the birth date in her tribute to her grandfather (which I am including in a list of biographies written by friends or family), I have had to do a little research.
I resisted looking first at Wikipedia. Instead I tried the biographical databases from both Gale and EBSCO. Neither even includes Goldman, which I found interesting. Fisher suggests that her grandfather (son of Goldman Sachs founder Marcus Goldman) was written out of most corporate histories because he vocally supported the German cause during World War I. He also did not appear in The Encyclopedia of World Biography, the World Book Encyclopedia, or the Funk and Wagnall's New World Encyclopedia. So, I returned to Wikipedia, where I found Goldman mentioned without dates. Then I just tried a general search of the Internet without luck.
Remembering my roots as a reference librarian, I logged into the New York Times Historical 1851-2006 database, to which I have access as a library card holder of the College of DuPage. There I found an article and an obituary for Henry Goldman stating that he was born September 21, 1857.
It still helps to have authoritative sources.