Robuta

https://www.aanda.org/articles/aa/abs/2003/17/aa3244/aa3244.html Spectroscopic observations of two proto planetary-nebulae candidates: SS73 56 & Hen 2-79 |... proto planetary nebulae https://www.aanda.org/articles/aa/abs/2010/12/aa15585-10/aa15585-10.html Photodissociation in proto-planetary nebulae - Hydrodynamical simulations and solutions for... proto planetary nebulaephotodissociationhydrodynamicalsimulationssolutions https://www.aanda.org/articles/aa/ref/2004/31/aa0461-04/aa0461-04.html Polarimetric observations of OH masers in proto-planetary nebulae | Astronomy & Astrophysics (A&A) proto planetary nebulaeoh masers