Columbia University [Class at Columbia.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class in a lecture hall.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Three professors.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Lecture hall.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]