_:n23f6dd7a10d048f7be44db14b1e61e1exb0
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://ocw.mit.edu/courses/6-011-introduction-to-communication-control-and-signal-processing-spring-2010/resources/mit6_011s10_quiz02/>