Paun, Gheorghe (2002). «II. Prerequisites». Membrane Computing: An Introduction(en inglés). Nueva York: Springer-Verlag. ISBN3540436014. Consultado el 24 de junio de 2012. «The parallelism with a computer, as we know computers in their general form, is clear: the code of a Turing machine is its program, the strings to be recognized represent the input data, and the universal Turing machine is the computer itself, with the instructions of the universal Turing machine corresponding to the operating system of a computer.»