CREATE TABLE table_8544 ("Tournament" CLOB, "Surface" CLOB, "Week" CLOB, "Winner and score" CLOB, "Finalist" CLOB, "Semifinalists" CLOB)

Which Surface has a Semifinalist of stefan edberg thomas muster?
SELECT "Surface" FROM table_8544 WHERE "Semifinalists" = 'stefan edberg thomas muster'
SELECT "Surface" FROM "table_8544" WHERE "Semifinalists" = 'stefan edberg thomas muster'