The past perfect tense (including contrast with past simple)
By:  C. E. Nuttall, S. D. Anderson, J. P. B. Shepherd. Students' book.
Contributors: Anderson, S. D.; Shepherd, J. P. B.; British Council.
Series: English language units -- unit 6
Publisher: Longman for the British Council
Published: 1969
Place of publication: London
Language: eng