Simplify the following text for a Grade 6 native English-speaking person.
Original: Additionally , the core collection has major works of art donated by Paul Mellon , Ailsa Mellon Bruce , Lessing J. Rosenwald , Samuel Henry Kress , Rush Harrison Kress , Peter Arrell Brown Widener , Joseph E. Widener and Chester Dale .
Simplified: Andrew W. Mellon gave money and art to help the museum . Many lovers of art have given the National Gallery their art collections , like Lessing J. Rosenwald , Samuel H. Kress , and Joseph E. Widener .