Questioning the Purity of the ZZ Ceti Instability Strip
Proceedings article published in 2005 by
A.~S Mukadam,
D.~E Winget,
T. von Hippel,
M.~H Montgomery 
,
S.~O Kepler,
A.~F.~M Costa
,
S.~O Kepler,
A.~F.~M Costa
