https://archive.org/details/top-welt-11-geheimnisse-bei-denen-die-nasa-nicht-will-dass-wir-es-wissen
https://archive.org/details/discovery-secret-underground-verborgene-geheimnisse-atlantis-hochkultur-in-nordamerika
https://archive.org/details/enzyklopaedie-wage-es-weise-zu-sein-im-lauf-der-zeit-arte
https://archive.org/details/max-bentow-der-mondscheinmann