You can google for the key terms: "programmed instruction" and "programmed learning". These were popular, I loved them too. I remember some had a tear-out flap

You can google for the key terms: "programmed instruction" and "programmed learning". These were popular, I loved them too. I remember some had a tear-out flap so you could hide the answer while you're reading the text! The Little Schemer uses programmed instruction.