Este livro tem uma dupla finalidade - auxiliar o estudante a melhor compreender e fixar o conceitos da Teoria Elementar da Música e evitar que o professor dispenda um tempo precioso ao ser obrigado a escrever exercícios no quadro negro (em classes coletivas) ou no caderno do aluno (em aulas individuais).
Various is the correct author for any book with multiple unknown authors, and is acceptable for books with multiple known authors, especially if not all are known or the list is very long (over 50).
If an editor is known, however, Various is not necessary. List the name of the editor as the primary author (with role "editor"). Contributing authors' names follow it.
Note: WorldCat is an excellent resource for finding author information and contents of anthologies.