Who was the Cover model when the Centerfold Model was Marketa Janska?
CREATE TABLE "2003" (
  "date" text,
  "cover_model" text,
  "centerfold_model" text,
  "interview_subject" text,
  "20_questions" text
);
SELECT "cover_model" FROM "2003" WHERE "centerfold_model"='marketa janska';