Columbia University [Three professors talking in front of a chalkboard.]

Columbia University [Three professors talking in front of a chalkboard.]

Columbia University [Three professors in front of a chalkboard.]

Columbia University [Three professors in front of a chalkboard.]

Columbia University [Three professors talking in front of a chalkboard.]

Columbia University [Three professors in front of a chalkboard.]

Columbia University [Three professors in front of a chalkboard.]

Columbia University [Two men talking.]

Columbia University [Professor at a desk.]

Columbia University [Professor at a desk.]

Columbia University [Professor at a desk.]

Columbia University [Three professors talking in the front of a classroom.]

Columbia University [Three professors talking in the front of a classroom.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]

Columbia University [Professor talking to a student.]

Columbia University [Professor with students in an office.]

Columbia University [Professor with students in an office.]

Columbia University [Professor teaching a class.]

Columbia University [Professor teaching a class.]