Which preposition to use with crux

of Occurrences 28%

The real causes were constitutional and personal; and the actual crux of the question was one of payment for defence.

in Occurrences 3%

Crux in recordatione passionis et mortis, quam in cruce ligni simplice Christus passus est pro nobis.

to Occurrences 2%

The air was darkened by hurtling parodies, the arrangement of which is still a standing crux to the bibliographers.

by Occurrences 1%

It is the crux by which society is tested.

Which preposition to use with  crux