APA

Hawthorn P., Marks A., . (1991). Easy keyboard tunes. London: Usborne.

Chicago

Hawthorn Philip, Marks Anthony, . 1991. Easy keyboard tunes. London: Usborne.

Harvard

Hawthorn P., Marks A., . (1991). Easy keyboard tunes. London: Usborne.

MLA

Hawthorn Philip, Marks Anthony, . Easy keyboard tunes. London: Usborne. 1991.