BIBLIOGRAPHY CONTRIBUTOR H.-R. Singer First name H.-R. Last name Singer Bibliography entries by this contributor Singer, H.-R. 1991. “Ibn Baškuwāl”. In Lexikon Des Mittelalters, 5:313. München; Zürich: Artemis & Winkler. Singer, H.-R. 1991. “Ibn Ḫaldūn”. In Lexikon Des Mittelalters, 5:316-317. München; Zürich: Artemis & Winkler. Singer, H.-R. 1991. “Ibn Ḥazm”. In Lexikon Des Mittelalters, 5:318. München; Zürich: Artemis & Winkler.