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White dwarf pulsators (ZZ Ceti variables) occur in the extension of the radial pulsation envelope ionization instability strip to the observed luminosities of 3 × 10−3 L⊙ according to van Horn (1979). Investigations have been underway to see if the driving mechanisms of hydrogen and helium ionization can cause radial pulsations as they do for the Cepheids, the RR Lyrae variables, and the δ Scuti variables...