\Bibitem{Iha70} \by Ya.~Ihara \paper On congruence monodromy problems.~I \jour Matematika \yr 1970 \vol 14 \issue 4 \pages 48--77 \mathnet{http://mi.mathnet.ru/mat554} \mathscinet{https://mathscinet.ams.org/mathscinet-getitem?mr=0289518} \zmath{https://zbmath.org/?q=an:0228.14009}