Aunt Jane's Nieces In The Red Cross by L. Frank Baum

The 10th and final book in the series for adolescent girls sees two of the three cousins react to atrocities in World War I by volunteering in the Red Cross. Written under the pseudonym of Edith Van Dyne, this is the 1915 version, which reflects United States' neutrality. A later version, published in 1918, differed significantly to reflect changes in the position of the United States.