Rolling Curves: An Old Proof of the Roulette Lemma. - Ulrich Abel; Linda Beukemann; Vitaliy Kushnirevych (Am. Math. Mon., 2017)

Convergence of linking Baskakov-type operators. - Ulrich Abel; Margareta Heilmann; Vitaliy Kushnirevych (Period. Math. Hung., 2020)

Reducing Multiple Integrals of Beukers's Type. - Ulrich Abel; Vitaliy Kushnirevych (Am. Math. Mon., 2020)