valuation of the sources of Toosis book of Al-Geybah

Sheikh Toosis book of Geyba (Occultation) is one of the precious heritages from Imams that have been originated from weighty and authentic origins. Today, we are heirs of this unique and matchless treasure that is considered truly as one of the most appropriate praiseworthy Hadith references.
In composing this book, Sheikh Toosi is benefited from very reliable sources of Shiite and organized its foundations that some parts of it are available for us today and unfortunately the other parts are not so.
In this writing, we are to find the major sources of Toosis book of Al-Geybah and we try our best to etymologize the compatible relationship between the origins and the book of al-Geybah and also to present its state of adoption.