SOURCE-17461Research NeededProbable
Walerian Meysztowicz, ed., “Manuscriptum Gertrudae Filiae Mesconis II Regis Polo...
Full citation
Walerian Meysztowicz, ed., “Manuscriptum Gertrudae Filiae Mesconis II Regis Poloniae,” Antemurale 2 (Rome: Institutum Historicum Polonicum, 1955), prayers 18 & 86.