Keywords
adult, adults, alone, artificial light, blackboard, blackboards, book, books, casual, casual wear, caucasian, chalk, claudia göpperl, clever, cleverness, close-up, close-ups, color image, colour image, copy space, daylight, drawing, education, european style, geometry, hand, hands, horizontal, indoors, instructing, instructor, instructors, knowledge, male, man, mathematics, men, one, people, person, photography, research, researcher, researchers, school, schools, science, sciences, scientist, scientists, teacher, teachers, teaching, textbook, textbooks, triangle, unsharp foreground, stock image, images, royalty free photo, stock photos, stock photograph, stock photographs, picture, pictures, graphic, graphics, fine art prints, print, poster, posters, mural, wall murals, 012793bl