What is the visitor team on April 4?
CREATE TABLE "chicago_black_hawks_4_st_louis_blues_1" (
  "date" text,
  "visitor" text,
  "score" text,
  "home" text,
  "record" text
);
SELECT "visitor" FROM "chicago_black_hawks_4_st_louis_blues_1" WHERE "date"='april 4';