https://archive.org/details/alex-north-der-schattenmoerder
https://archive.org/details/spinoza-das-abenteuer-der-diesseitigkeit-dr.-phil.-mathias-jung
https://archive.org/details/jochen-kirchhoff-nietzsche-und-die-grosse-gesundheit
https://archive.org/details/top-welt-10-geheimnisse-die-sich-in-bekannten-kunstwerken-verstecken