[1] A. Ostrowski: Über die Absolutabweichung einer differentiebaren Funktion von ihrem Integralmittelwert. Comment. Math. Helv. 10 (1938), 226–227. DOI 10.1007/BF01214290 | MR 1509574

[2] G. S. Mahajani: A note on an inequality. Math. Student 6 (1938), 125–128.

[3] K. S. K. Iyengar: Note on an inequality. Math. Student 6 (1938), 75–76.

[4] G. V. Milovanovič: On some integral inequalities. Univ. Beograd. Publ. Elektrotehn. Fak. Ser. Mat. Fiz. 498–541 (1975), 119–124. MR 0385044

[5] G. V. Milovanovič: On nekim funcionalnim nejednakostim. Univ. Beograd. Publ. Elektrotehn. Fak. Ser. Mat. Fiz. 599 (1977), 1–59.

[6] G. V. Milovanovič and J. E. Pečarić: On generalizations of the inequality of A. Ostrowski and some related applications. Univ. Beograd. Publ. Elektrotehn. Fak. Ser. Mat. Fiz. 544–576 (1976), 155–158. MR 0457648

[7] G. V. Milovanovič and J. E. Pečarić: Some considerations on Iyengar’s inequality and some related applications. Univ. Beograd. Publ. Elektrotehn, Fak. Ser. Mat. Fiz. 544–576 (1976), 166–170. MR 0447509

[8] G. C. Lorenz: Approximation of Functions. Holt, Rinehart and Winson, New York, 1966. MR 0213785