 By the 13th and 14th centuries the "ministeriales" formed an intrinsic part of the lower nobility, and in the 15th century formed the core of the German knightly class ("Ritterstand").Other regions were not as open, for as late as the fifteenth century the documents of the Dutch province of Gelderland continued to distinguish between knights of noble and of ministerial birth.Legally, a ministerial was a ministerial, bound by the rights and duties enumerated in their area.