let helm_ns = Gdome.domString "http://www.cs.unibo.it/helm"
let xlink_ns = Gdome.domString "http://www.w3.org/1999/xlink"
let mathml_ns = Gdome.domString "http://www.w3.org/1998/Math/MathML"
let helm_ns = Gdome.domString "http://www.cs.unibo.it/helm"
let xlink_ns = Gdome.domString "http://www.w3.org/1999/xlink"
let mathml_ns = Gdome.domString "http://www.w3.org/1998/Math/MathML"