Institut für Sexualwissenschaft (partially found library content; 1933 and earlier)
The Institut für Sexualwissenschaft (Institute for Sex Research) was a privately-owned scientific sexual studies institute in Berlin, founded and lead by Magnus Hirschfield. Established in 1919, the institute provided one of the earliest such libraries into sexual research in the world, housing over 20,000 volumes. The institute was also linked to Hirschfield's Scientific-Humanitarian Committee, which, founded in 1897, was the world's first known LGBT rights organization, and the library featured some of the world's earliest research into transgender people. The institute also ran counseling and medical consultations, attracting people from all over Europe.
However, the period of relative tolerance in Weimar Republic-era Germany did not last. As the Nazi Party came to power in 1933, it launched a purge of gay clubs and activist groups in Berlin. On 6 May 1933, the institute was raided by the Nazi-affiliated German Student Union. Days later, the contents of the institute's library and archive were publically burned on 10 May, as part of the Nazis first ever mass public book burning. Thousands of documents and photographs were lost. 
Following the war, West German courts ruled that the Nazi attack and destruction of the institute was legal, and even retained Nazi amendments to the legal code that further persecuted homosexuality. No legal restitution was made for the damage, and a new institute with the same name was not re-established until 1973. Most of the texts contained within remain lost to this day. Today, the Magnus Hirschfeld Society has a page on its website listing wanted texts and items from the archive, alongside some that have been recovered. Some surviving documents are today preserved at the ONE National Gay & Lesbian Archives in California and the Haeberle-Hirschfeld-Archive of Sexology in Berlin.
- Magnus Hirschfield Society - The first Institute for Sexual Science (1919-1933) Retrieved 23 Sept '18
- LGBTQ Institute in Germany Was Burned Down by Nazis Retrieved 23 Sept '18
- I keep hearing that during the Nazi book burnings, the Institute of Sexology's research on transsexuality was burned and destroyed. To what degree was that research, if it existed, lost? Was the Institute's research (all of it) preserved anywhere? - /r/AskHistorians Retrieved 23 Sept '18