doctor, scientist, scholar, art historian; purchased Raphael's Sistine Madonna (c. 1512-14), in 1753 for the Dresden Gemäldegalerie, wrote important monographs on Piranesi (1779), Mengs ( 1780) and antiquarian work, Descrizione dei circhi particolarmente di quello di Caracalla (1789).

Print collector, medical doctor; surgeon. Bierens de Haan was the son of David Bierens de Haan, professor of mathematics and physics at Leiden University, and Johanna Catharina Justina IJssel de Schepper. The young Bierens de Haan attended the Leiden gymnasium and, from 1887 to 1894, he studied medicine at Leiden University. He also received training in hospitals and universities abroad, in particular in Bonn, Vienna, Paris, and London. In those years he began building up his print collection, while visiting the European print rooms.

Historian of Portuguese art and medical doctor; successor to José de Figueiredo at the Academia de Belas Artes, Lisbon. Santos' parents were Clemente José dos Santos, a physician, and Maria Amelia dos Santos Pinheiro. His grandfather was Clement José dos Santos, Baron Santos Clemente. After secondary school, Santos entered the Medical-Surgical School of Lisbon in 1898, graduating in 1903.

Doctor; poet; archaologist; historian of Portuguese art; archival reasearch; standard source for Portuguese art history.

Early documents-style scholar of Dutch art, Medical Doctor. His work was succeeded by Frederik D. O. Obreen and Abraham Bredius. Van der Willigen was the son of the protestant minister (preacher) Pieter van der Willigen (1778-1847) and Christina Abigaël van Campen (d. 1827). After his studies in Medicine he settled in Haarlem as a Medical Doctor. From his uncle, Adriaan van der Willigen (1766-1841), he inherited an important art collection and library. Like his uncle, he was a lover of art and art history.