Architectural historian, architect and archaeologist; specialist in ancient excavations, and medieval German architecture. Adler attended the Berlin Kunstakademie beginning in 1841. In 1846 he continued at the University of Berlin (Bauakademie). From 1854 he taught there under Ferdinand von Arnim (1814-1856) and from 1859 as a Dozent for the history of architecture. He was made professor at the Akademie in 1861 succeeding in the position previously held by Wilhelm Lübke.

Early historian of medieval Christian art. Willibald Sauerländer included Martin among the "pantheon of great [early] art historians" of medieval art whose numbers included Adolphe Napoléon Didron, Charles Cahier, Ferdinand Piper and Franz Xaver Kraus.

University of Chicago medievalist; authored the Pelican History of Art volume on medieval art in Britain. Rickert was the daughter of Francis E. Rickert and Josephine Newburgh (Rickert). At the death of her mother, her older sister and later medieval literary scholar, [Martha] Edith Rickert (1871-1838) helped raise Margaret. The younger Rickert graduated from Grinell College, Iowa, in 1910 becoming a high school principal in Greene, Iowa. She made an initial trip to Europe in 1914 which consolidated her interest in art history.

Early scholar and illustrator of medieval Celtic art. Stokes was the daughter of William Stokes (1804-1878), a physician, and Mary Black (Stokes). Her paternal grandfather was Whitley Stokes (1763-1845) a physician and author of an English-Irish dictionary. Her father's friends included the archaeologists and scholars James Henthorn Todd (1805-1869), George Petrie (1790-1866), William Reeves (1815-1892), Sir Samuel Ferguson (1810-1886), and Edwin R. W. Quin (1812-1871), third earl of Dunraven; these family friends inspired an interested in archaeology.

Director of the Karlsruher Kunsthalle (Art Gallery). When hospitalized in 1925, his assistant Hans Curjel temporarily replaced him.