\Bibitem{Bus66} \by H.~Busemann \paper On Hilbert's fourth problem \jour Russian Math. Surveys \yr 1966 \vol 21 \issue 1 \mathnet{http://mi.mathnet.ru//eng/rm5825} \mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=198376} \zmath{https://zbmath.org/?q=an:0156.43303}