let mathmlns = "http://www.w3.org/1998/Math/MathML";;
let xmldiffns = "http://helm.cs.unibo.it/XmlDiff";;
let helmns = "http://www.cs.unibo.it/helm";;
let mathmlns = "http://www.w3.org/1998/Math/MathML";;
let xmldiffns = "http://helm.cs.unibo.it/XmlDiff";;
let helmns = "http://www.cs.unibo.it/helm";;