Ключевые слова: abstract, aged, algebraic, alphabet, ancient, background, blur, book, brown, brownish, close, detail, details, english, entry, faded, flip, front, handbook, knowledge, language, learn, learning, manual, material, mathematics, notebook, old, open, page, pages, pale, paper, radical, school, schooling, science, sign, study, text, tinge, vintage, word, words, written, yellow, yellowed,