* read what we have made in Astrophysics of Gals (Kartunnen book or other) for 21cm observations in Our Galaxy
* https://vale.oso.chalmers.se/salsa/welcome
*https://vale.oso.chalmers.se/salsa/support for "Mapping the Milky Way" and the paper "Mapping the Spiral Structure of..." by T.R. Santo and S. A. Uddin, International Journal of Astronomy, 2013, 2(3):37
