Appling, William D. “Approximate Set Function Measurability Decomposition and Range Union Inclusion”. Anal. Numér. Théor. Approx. 19, no. 2 (August 1, 1990): 93–104. Accessed April 15, 2025. https://ictp.acad.ro/jnaat/journal/article/view/1990-vol19-no2-art1.