APA (7th ed.) Citation

Enid Blyton. (2018). The Secret Seven, Mystery of the Skull (2018.). Hodder Children's book.

Chicago Style (17th ed.) Citation

Enid Blyton. The Secret Seven, Mystery of the Skull. 2018. Hodder Children's book, 2018.

MLA (9th ed.) Citation

Enid Blyton. The Secret Seven, Mystery of the Skull. 2018. Hodder Children's book, 2018.

Warning: These citations may not always be 100% accurate.