Hi!
For tessellated mesh conversion this is a great article: Polygonal Mesh to B-Rep Solid Conversion: Algorithm Details and C++ Code Samples / Habr The same author has a more detailed white paper, too.
For scanned objects I’m not a big fan of NURBS based reconstruction since the result is not more editable or precise, just smooth. There are commercial tools that capable of precise b-rep reconstruction, like Geomagic Studio, but still not automatic. This paper from Tamas Varady and his colleagues explains the basics of it, and essentially every reverse engineering system uses this method. Algorithms for reverse engineering boundary representation models - ScienceDirect