Letters that make written material
a, e, l, n, m, r, t, i, w are letters that make 'written material'
Words within written material
ER, IT, writ, rial, MA, MAT, te, ma, mater, at, en, RI, mA, TT, mat, material, ten, written, mate, AL, IA, Ate, Al, At, Er, Te are words within 'written material'