Complex sentence: Her accomplishment was declared a "Grand Slam" by Philippe Chatrier, president of the International Tennis Federation, however some tennis observers countered that it was not a true slam because the titles had not been won in a single calendar year.
Split into simpler sentences: Her accomplishment was declared a "Grand Slam" by Philippe Chatrier, president of the International Tennis Federation. Some tennis observers, however, countered that it was not a true slam because the titles had not been won in a single calendar year.