@article{JCA_2014_21_2_JCA_2014_21_2_a5,
     author = {J. W. Helton and S. McCullough},
     title = {Free {Convex} {Sets} {Defined} by {Rational} {Expressions} {Have} {LMI} {Representations}},
     journal = {Journal of convex analysis},
     pages = {425--448},
     publisher = {mathdoc},
     volume = {21},
     number = {2},
     year = {2014},
     url = {http://geodesic.mathdoc.fr/item/JCA_2014_21_2_JCA_2014_21_2_a5/}
}