Book Sales Catalogues Online offers a comprehensive bibliography of book sales catalogues printed in the Dutch Republic before 1801, providing full access to some 4,000 digital facsimiles from ca. 50 libraries across Europe. These catalogues are a key primary source for research on the history of the book and libraries, the history of ideas, the history of collecting, the history of literature, and the history of art. The catalogues contain information on books from all over Europe in various languages, such as Dutch, French, and Latin.

The Digital Library of the Catholic Reformation makes the documentary riches of this era accessible, adding functionalities that maximize the flexibility with which researchers can search, view, organize, and manipulate this historically important source material. With new content uploads occurring on a regular basis, the database offers a constantly growing treasury of documents, including papal and synodal decrees, catechisms and inquisitorial manuals, biblical commentaries, theological treatises and systems, liturgical writings, saints' lives, and devotional works.

The Digital Library of Classic Protestant Texts gives researchers access to an extensive range of seminal works from the Reformation and post-Reformation eras. With new content uploads occurring on a regular basis, the database offers a constantly growing treasury of theological writings, biblical commentaries, confessional documents, and polemical treatises written by more than 300 Protestant authors.

Facsimile edition of the "Patrologia Graeca", edited by Jacques-Paul Migne from 1857 to 1866 in more than 160 volumes. The database comprises works of the Greek church literature beginning with Pseudo-Clemens (100 AD) up to Kallistos (1478) and thus makes available the important Greek Christian authors and the most influential works of theology, philosophy, history and literature of the late ancient world and the early Middle Ages. Texts are made easily accessible by an index of contents in Latin and Greek language, by an index of authors, a title index and an index of subject. All of these indexes are full text ones.