APA

Yam P., Lee J., . (2012). Primary level vocabulary & usage. Book 6. Singapore: SAP Group.

Chicago

Yam Peter, Lee J, . 2012. Primary level vocabulary & usage. Book 6. Singapore: SAP Group.

Harvard

Yam P., Lee J., . (2012). Primary level vocabulary & usage. Book 6. Singapore: SAP Group.

MLA

Yam Peter, Lee J, . Primary level vocabulary & usage. Book 6. Singapore: SAP Group. 2012.