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

### Instruction:
Name the mixed doubles for year before 1991 and men's doubles of david jepson buck ryan

### Inputs:
table_name: table, columns: ['Year', "Men's singles", "Women's singles", "Men's doubles", "Women's doubles", 'Mixed doubles']

### Response:
SELECT Mixed doubles FROM table WHERE Year < 1991 AND Men's doubles = david jepson buck ryan