The Riccati-Pade Schr\"{o}dinger-eigenvalue algorithm (RPM,
explained in the paper) belongs to my favored ones. It is purely
empirical (i.e., as far as I know, the underlying idea is not based
on any rigorous proof of validity yet) but its many times tested
numerical efficiency is simply amazing. The paper brings a new
support of this experience. This time, using sextic oscillators for
illustration, the computation of resonances in multiple wells is
shown to give results which are fully compatible with the results of
other methods.

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MR2435929 Fernández, Francisco M. The accurate calculation of resonances in multiple-well oscillators. J. Phys. A 41 (2008), no. 6, 065202, 5 pp. 81Q10 (47N50 65L15 81-04)