Holomorphic automorphisms of Danielewski surfaces II -- structure of the   overshear group
  We apply Nevanlinna theory for algebraic varieties to Danielewski surfaces and investigate their group of holomorphic automorphisms. Our main result states that the overshear group which is known to be dense in the identity component of the holomorphic automorphism group, is a free amalgamated product. 
Rafael B. Andrist, Frank Kutzschebauch and Andreas Lind
math.CV