Jansen, Thomas (1998), «Introduction to the Theory of Complexity and Approximation Algorithms», en Mayr, Ernst W.; Prömel, Hans Jürgen; Steger, eds., Lectures on Proof Verification and Approximation Algorithms, Springer, pp. 5-28, ISBN9783540642015, doi:10.1007/BFb0053011.. See discussion following Definition 1.30 on p. 20.
doi.org
dx.doi.org
Jansen, Thomas (1998), «Introduction to the Theory of Complexity and Approximation Algorithms», en Mayr, Ernst W.; Prömel, Hans Jürgen; Steger, eds., Lectures on Proof Verification and Approximation Algorithms, Springer, pp. 5-28, ISBN9783540642015, doi:10.1007/BFb0053011.. See discussion following Definition 1.30 on p. 20.