Label of a Hilbert modular surface (awaiting review)

The label of a Hilbert modular surface is of the form F-N-b-t where

• F is a number field label for the base field;

• N is an ideal label for the level;

• b is an ideal label for the component ideal;

• t is the type of the congruence subgroup.

The value for t can be either sl-0 or gl-0 to indicate the congruence subgroup.