Оригинал: Alfred's Essentials of Music Theory Software, Version 2.0, Volumes 2 & 3. Composed by Andrew Surmani and Morton Manus. Theory.
Превод: Essentials на Алфред на Music Theory Software, Version 2.0, Volumes 2. Andrew Surmani. Възпитател Version. Справочни ръководства. Теория.