I got the Dificiles book on Amazon. It is currently listed as unavailable. The full name is "Difíciles eran las de antes : historia de las figuritas de fútbol en la Argentina :1910-2013" by Bitrán, Rafael, and Chiappini, Francisco.
Here is a link to the publisher:
http://www.olmoediciones.com/shop/pr...-las-de-antes/
Here is a web site with images from a museum show devoted to Argentinean soccer cards that Bitran was involved with:
https://www.tiempoar.com.ar/nota/una...n-cada-mundial
Here is a video on the show:
https://youtu.be/lj8TtiMW0ec