Original sentence: In their book, The Genesis of the Memorial Day Holiday in America, Bellware and Gardiner assert that the national Memorial Day holiday is a direct offshoot of the observance begun by the Ladies Memorial Association of Columbus, Georgia in 1866
Edited sentence: In their book, The Genesis of the Memorial Day Holiday in America, Bellware and Gardiner determine that the national Memorial Day holiday is a direct offshoot of the observance begun by the Ladies Memorial Association of Columbus, Georgia in 1866