Mock, V. E. (1982). Subtraction drill for levels 1-3. David S. Lake Publishers.
Cita Chicago Style (17a ed.)Mock, Valerie E. Subtraction Drill for Levels 1-3. Belmont, Calif: David S. Lake Publishers, 1982.
Cita MLA (9a ed.)Mock, Valerie E. Subtraction Drill for Levels 1-3. David S. Lake Publishers, 1982.
Precaución: Estas citas no son 100% exactas.