Most people do not know which river or creek the fishes are captured. Neither do the shop owner since it typically goes through one or more distribution channels. We just see and buy !
Have a heck of time trying to identify them correctly and need to constantly reference to a few books. One of the clearer books i have is from famous Ian A. M. Fuller & Hans-Georg Evers "Identifying Corydoradinae Catfish". I got Ian signature in it numbered 041. Yeah !
I do not believe the book is widely available since is quite specialise and relatively expensive. If you read this article and manage to buy one after, please let them know i helped to introduce the book to you !