Mocanu, P. T., D. Ripeanu, and I. Şerb. “On the Order of Starlikeness of Convex Functions of Order \(\alpha\)”. Anal. Numér. Théor. Approx., vol. 10, no. 2, Aug. 1981, pp. 195-9, https://ictp.acad.ro/jnaat/journal/article/view/1981-vol10-no2-art8.