Among these, the work that has dominated Abhidhamma studies from about the twelfth century to the present day is the first mentioned, the Abhidhammattha Sangaha, "The Compendium of Things contained in the Abhidhamma." Its popularity may be accounted for by its remarkable balance between concision and comprehensiveness. Within its short scope all the essentials of the Abhidhamma are briefly and carefully summarized. Although the book's manner of treatment is extremely terse even to the point of obscurity when read alone, when studied under a qualified teacher or with the aid of an explanatory guide, it leads the student confidently through the winding maze of the system to a clear perception of its entire structure. For this reason throughout the Theravada Buddhist world the Abhidhammattha Sangaha is always used as the first textbook in Abhidhamma studies. In Buddhist monasteries, especially in Burma, novices and young bhikkhus are required to learn the Sangaha by heart before they are permitted to study the books of the Abhidhamma Pitaka and its Commentaries