1973 U.S. Professional Indoor – Singles

Rod Laver was the defending champion, but lost in the quarterfinals this year. Stan Smith won the title, defeating Robert Lutz 7–6(7–2), 7–6(7–5), 4–6, 6–4 in the final.

Source: Wikipedia DBpedia

What is 1973 U.S. Professional Indoor – Singles subject of?

1973 U.S. Professional Indoor – Singles is subject of U.S. Pro Indoor and 1973 Grand Prix (tennis).