Isidore acknowledges Pliny , but not his other principal sources , namely Cassiodorus , Servius and Solinus .
The Etymologies summarized and organized a wealth of knowledge from hundreds of classical sources ; three of its books are derived largely from Pliny the Elder 's Natural History .
Isidore acknowledges Pliny the Elder , but not his other principal sources , namely Cassiodorus , Servius and Solinus .
The Etymologies summarized and organized a wealth of knowledge from hundreds of classical sources ; three of its books are derived largely from Pliny the Elder 's Natural History .