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You can find all my eBooks online, both in English and in Spanish, at "Smashwords Publishers."
I recommend that you read them in PDF format, either after downloading them from the web or reading them directly online with your browser.
For now, they are all free.
Some of them deal with astronical themes, others are about other topics. To see a list of my eBooks, please click/tap on the following image. When the online publisher's page appears, scroll down and you'll find the list of my books. Most titles can be read either in English or Spanish.