Marganitha

The Marganitha (, "Pearl") is a book summarising the doctrine of the Assyrian Church of the East written by Mar Odisho, Metropolitan of N’siwin and Armenia, in 1298. The website of the Assyrian Church calls the "Marganitha" the "official manual of the faith of the Church of the East". The explanation of the author for naming the book as Margānītā (Pearl) is as follows: “I […] wrote this book, small in size and brief, but extensive in its subject matter. Hence, I have called it “The Pearl”, the truth of Christianity; and herein I have briefly treated of the origin, roots, plants and branches of the teaching of the Church” . 
Structure.
The book is divided in four parts:
The first part is theological, explaining God's necessary existence and most basic features, as revealed in the Old Testament. Following this is the Assyrian cosmology, which sets the stage for the coming of the Messiah. The next part is Christological, attempting to explain the Assyrian understanding of Jesus' personhood and divinity; this is the most crucial part in terms of explaining Assyrian doctrine to other Christian groups, as the Assyrians had been incorrectly labeled Nestorians for centuries. The thrust of this section is largely ecumenical, in an attempt to reconcile the linguistic and cultural forces that kept the Assyrians from the larger Christian community. The final division concerns the practice and significance of Christian sacraments. An appendix of the Assyrian patriarchs often follows the text of the book.