\Bibitem{1} \paper To the 70th birthday of Professor V.\,I.~Burenkov \jour Eurasian Math. J. \yr 2012 \vol 3 \issue 3 \pages 7--10 \mathnet{http://mi.mathnet.ru/emj93} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=3024127}