I want to know the answer to the following question:
What book is considered to be the source of many Orthodox beliefs regarding Mary?
All the background I'm provided with is that "The Orthodox believe that Mary was instrumental in the growth of Christianity during the life of Jesus, and after his Crucifixion, and Orthodox Theologian Sergei Bulgakov wrote: "The Virgin Mary is the center, invisible, but real, of the Apostolic Church."". Is that enough to answer the question?