A Second Serve That's Just as Big as the First - The New York Times
What are the 'first serve' and 'second serve' in tennis? - Quora
Developing The 2nd Serve In Tennis - Tenicity
How to Master the SECOND SERVE | tennis | The first serve gets all the glory, but the second serve is equally - if not MORE - important to develop. Here's how
How to hit a SECOND SERVE - YouTube
Tennis Serve: Key Differences Between The 1st and The 2nd Serve - YouTube
How To Hit Reliable Second Serves Under Pressure | Feel Tennis
How To Hit The Perfect 2nd Serve in Tennis - Slice vs Flat vs Kick Tennis Serve Lesson - YouTube
TENNIS SERVE | How To Improve Your Second Serve - YouTube