Obee B. Bob & Evans V. Virginia. (2008). Upstream. Upper-Intermediate B2+: Workbook: Student's Book. Newbury, Express Publishing, 2008.
Chicago-viite (17. p.)Obee B. Bob ja Evans V. Virginia. Upstream. Upper-Intermediate B2+: Workbook: Student's Book. Newbury, Express Publishing, 2008, 2008.
MLA-viite (9. p.)Obee B. Bob ja Evans V. Virginia. Upstream. Upper-Intermediate B2+: Workbook: Student's Book. Newbury, Express Publishing, 2008, 2008.
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