\Bibitem{Kuz54} \by G.~E.~Kuzmak \paper On a~system of functions \jour Sb. Math. \yr 1954 \vol 77 \issue 3 \mathnet{http://mi.mathnet.ru//eng/sm5284} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=65683} \zmath{https://zbmath.org/?q=an:0057.29902}