From the notes of Mirjam Wirz:
MIHCK
Mahler in the National Library
The National Library is as well-guarded as the National Bank. There is no way to get around the security guards. They snub me in Russian, which I don't understand. Finally they call a security guard from the third floor who speaks English. This seems to be a welcome change for him. He shows me the lockers in the basement and in answer to my question, if I can take a camera into the library, he advises me to smuggle it under my belt through the security gates. When this is done, he invites me to visit him on the third floor during my tour through the library.