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The leitner system has been invented in 1970 https://en.wikipedia.org/wiki/Leitner_system

but Adaptively-spaced repetition which is the base of Leitner system has been registered in google patents in 2012 here http://www.google.com/patents/US20120322043

the first question is "everything in google patents page is really patented ?" and the second question is "I've developed an application which works based on Leitner systems ,now I'm wondering if I'm breaking the law or not?"

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Documents of the type USYYYY1234567 (where YYYY is a year and 1234567 is a sequence of numbers) are not patents, but rather pre-grant publications of patent applications. The application in question (serial number 13/163297) has been abandoned and was not granted as a patent.

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