كتاب ذو غلاف ورقي
- Fischer، Steven Roger (2004). History of Reading. Globalities Series. Reaktion Books. صفحة 282. ISBN 9781861892096. اطلع عليه بتاريخ 17 فبراير 2013.
[...] in 1867, with the coming into force of the constitution of the Northern German Federation [...], works by German authors deceased for 30 years or more officially became public domain. Entire libraries of very cheap paperback editions of German classics immediately flooded the market. And so Reclam, too, extended his paperback idea with the new series 'Universal-Bibliothek' (Universal Library') [...]. Thousands of titles eventually followed, which included nearly all the world's great literature. In this way, and despite most Western countries' imitations, Reclam paperbacks became the world's foremost paperback series.
- The British Library – Aspects of the Victorian book نسخة محفوظة 16 سبتمبر 2017 على موقع واي باك مشين.
- Appelbaum، Yoni (10 September 2014). "Publishers Gave Away 122,951,031 Books During World War II". The Atlantic. مؤرشف من الأصل في 26 مايو 2018.