book Albert Moll Untersuchungen über die Libido sexualis Investigations Concerning the Libido Sexualis 1897 https://archive.org/details/bub_gb_4kTJAAAAMAAJ/ https://catalog.hathitrust.org/Record/001353239 https://www.worldcat.org/oclc/563818530 Untersuchungen über die Libido sexualis Investigations Concerning the Libido Sexualis