Complex sentence: In addition to the White House, Parish's clients included the philanthropist Jane Engelhard and the socialite and art collector Betsey Cushing Roosevelt Whitney, Annette de la Renta, Alice Rogers, Mrs. Charles Percy, were also clients.
Split into simpler sentences: In addition to the White House, Parish's clients included the philanthropist Jane Engelhard and the socialite and art collector Betsey Cushing Roosevelt Whitney. Annette De La Renta, Alice Rogers, Mrs. Charls Percy, were also clients.