How can you tell if a book is Orthodox.?!.Saint Sophrony the Athonite.

Reference:

Saint Sophrony the Athonite talking about Saint Silouan. Essex Monastery, December 4th, 1989.

https://otelders.org/theology-and-spirituality/how-can-you-tell-if-a-book-is-orthodox-st-sophrony-talks-about-st-silouan-and-his-writings/