%0 Journal Article %A Kristijan Cafuta %A Igor Klep %A Janez Povh %T Rational sums of hermitian squares of free noncommutative polynomials %J Ars Mathematica Contemporanea %D 2015 %P 243-259 %V 9 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.26493/1855-3974.518.768/ %R 10.26493/1855-3974.518.768 %G en %F 10_26493_1855_3974_518_768