Invariance of the Length and the Area of Cycloids. - Hyounggyu Choi (Am. Math. Mon., 2020)

Concurrence of Three Area-Bisecting Cevians of a Triangle in Three Geometries. - Hyounggyu Choi; Kyeonghoon Jeong (Am. Math. Mon., 2021)

Invariance of the Area and Volume of Cycloid Surfaces and Trochoid Surfaces. - Hyounggyu Choi (Am. Math. Mon., 2023)