Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What reference, written by Nelson Riddle, suggests 2 violas?

### Inputs:
table_name: table, columns: ['Reference', 'Author', 'Section Size', 'Violins', 'Violas', 'Celli', 'Basses']

### Response:
SELECT Reference FROM table WHERE Violas = 2 AND Author = Nelson Riddle