Ob integralʹnykh funk︠t︡sionalakh s peremennoĭ oblastʹ︠i︡u integrirovani︠i︡a - Danil︠i︡uk, I. I. (Ivan Ilʹich), 1931 (Trudy Matematicheskogo instituta imeni V.A. Steklova ;, 1972)