Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_23235767_4 (year VARCHAR, opponent_in_the_final VARCHAR, surface VARCHAR, championship VARCHAR)
### Question:
Name the year for clay for boston and guillermo vilas
### Answer:
SELECT year FROM table_23235767_4 WHERE surface = "Clay" AND championship = "Boston" AND opponent_in_the_final = "Guillermo Vilas"