  The far-infrared spectra of circumstellar envelopes around various
oxygen-rich stars were observed using the ISO Long Wavelength Spectrometer
(LWS). We have examined high signal-to-noise ISO LWS observations of the
luminous supergiant star, VY CMa, with the aim of identifying all of the
spectral lines. By paying particular attention to water lines, we aim to
separate the lines due to other species, in particular, to prepare for
forthcoming observations that will cover the same spectral range using Herschel
PACS and at higher spectral resolution using Herschel HIFI and SOFIA. We have
developed a fitting method to account for blended water lines using a simple
weighting scheme to distribute the flux. We have applied this approach to
several other stars which we compare with VY CMa. We present line fluxes for
the unblended H2O and CO lines, and present detections of several possible
nu_2=1 vibrationally excited water lines. We also identify blended lines of OH,
one unblended and several blended lines of NH3, and one possible detection of
H3O+.
