Simplify the following text for a Grade 11 native English-speaking person.
Original: A second part , Pandectarium sive partitionum universalium Conradi Gesneri Ligurini libri xxi , appeared in 1548 ; only nineteen books being then concluded .
Simplified: A second part , Pandectarum sive partitionum universalium libri xxi , appeared in 1548 ; only nineteen books being then concluded .