  Double-mode RR Lyr type stars are important for studies of properties of
horizontal-branch stars. In particular, two periods coupled with spectral
properties give a mass estimate that is independent of evolutionary models.
Here, we present 59 new Galactic double-mode RR Lyr stars found in the LINEAR
survey data with the fundamental radial mode and the first overtone exited (RRd
stars). These stars may be useful for constraining the mass-metallicity
relation for field horizontal-branch stars. Also, new RRd stars found in the
LMC by EROS-II are verified. We present the updated Petersen diagram and the
distribution of the fundamental mode periods. Comments on selected variable
stars from LINEAR and LMC EROS-II surveys are also presented, including very
rare objects: the third known mode-switching RR Lyr and Cepheid pulsating
simultaneously in three radial modes.
