Task: Question Generation
Input (English): According to heraldic sources total number of legal ennoblements issued between the 14th century and the mid-18th century, is estimated at approximately 800. This is an average of only about two ennoblements per year or only 0.000 000 14 – 0.000 001 of historical population. Compare: historical demography of Poland.
Output (English): What type of sources give information regarding total number of enablements?