Abstract
Infrared spectra of the four planetary nebulae, NGC7027, BD+303639, NGC6153 and NGC6543 have been taken by the ISO Short Wavelength Spectrometer (SWS). These ISO data have been complemented with the already existing optical and ultraviolet observations. By comparing the nebular abundances for NGC7027 and BD+303639 with those given by new theoretical evolutionary models, the mass of the progenitor star of these nebulae has been constrained.
