  The ultraviolet spectra of all "weak emission line central stars of planetary
nebulae" (WELS) with available IUE data is analyzed. We found that the WELS can
be divided in three different groups regarding their UV: (1) Strong P-Cygni
profiles (mainly in C IV 1549); (2) Weak P-Cygni features and (3) Absence of
P-Cygni profiles. We have measured wind terminal velocities for all objects
presenting P-Cygni profiles in N V 1238 and/or C IV 1549. The results obtained
were compared to the UV data of the two prototype stars of the [WC]-PG 1159
class, namely, A30 and A78. They indicate that WELS are distinct from the
[WC]-PG 1159 stars, in contrast to previous claims in the literature. In order
to gain a better understanding about the WELS, we clearly need to determine
their physical parameters and chemical abundances. First non LTE expanding
atmosphere models (using the CMFGEN code) for the UV and optical spectra of the
star Hen 2-12 are presented.
