Fels, Gregor, and Wilhelm Kaup. “Local Tube Realizations of CR-Manifolds and Maximal Abelian Subalgebras”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE 10, no. 1 (March 28, 2011): 99-128. Accessed May 27, 2025. http://20.103.181.36/index.php/annaliscienze/article/view/228.