Betsis, Andrew. IELTS : the vocabulary files : English usage upper intermediate : students book : level b1 / Andrew Betsis, Lawrence Mamas. - United Kingdom : Global ELT. - 63 p. : ill. ; 298 cm. Score: 5.0 - 5.5 - 6.0. ISBN: 9781904663416 Subjects--Topical Terms: English language--usage.