APA

brandreth g., stevenson p., . (1981). challenge. london: trans world publishers ltd.

Chicago

brandreth gyles, stevenson peter, . 1981. challenge. london: trans world publishers ltd.

Harvard

brandreth g., stevenson p., . (1981). challenge. london: trans world publishers ltd.

MLA

brandreth gyles, stevenson peter, . challenge. london: trans world publishers ltd. 1981.