\Bibitem{Oss71} \by R.~Osserman \paper Minimal varieties \jour Matematika \yr 1971 \vol 15 \issue 2 \pages 104--125 \mathnet{http://mi.mathnet.ru/mat593} \mathscinet{https://mathscinet.ams.org/mathscinet-getitem?mr=0276875} \zmath{https://zbmath.org/?q=an:0188.53801} \transl \jour Bull. Amer. Math. Soc. \yr 1969 \vol 75 \pages 1092--1120