Ключевые слова: 60s, academic, adult, beard, blackboard, board, chalkboard, class, classroom, clever, coat, concentrate, conceptual, education, elderly, equation, exam, formula, glasses, graduate, idea, intelligent, knowledge, lecturer, lessons, look, male, man, math, mathematics, one, person, physics, portrait, profession, professor, school, science, scientific, senior, sight, study, subject, teach, teacher, university, white, wisdom, wise, write,