The lines have been taken originally from
(1) S. Thorwirth, H. S. P. Mueller, F. Lewen, R. Gendriesch, and G. Winnewisser,
Astron. Astrophys. 363 (2000) L37;
(2) T. Amano and Z. Zelinger, 
J. Mol. Spectrosc. 211 (2002) 273;
(3) R. A. Creswell, E. F. Pearson, M. Winnewisser, and G. Winnewisser,
Z. Naturforsch. A 31 (1976) 221;
(4) T. Okabayashi and M. Tanimoto,
J. Chem. Phys. 99 (1993) 3268.
In addition, IR transitions were taken from
(5) J. B. Burkholder, A. Sinha, P. D. Hammer, and C. J. Howard,
J. Mol. Spectrosc. 126 (1987) 72; and
(6) A. G. Maki and G. Ch. Mellau, 
J. Mol. Spectrosc. 206 (2001) 47.
Note: Uncertainties in (2) were deemed to be too conservative 
and had been adjusted.

The lines from (6) were not complete initially.
In the present data set, data measured in (1) and (2) 
were averaged and the uncertainties adjusted accordingly.
An excited state transition from (4) and two transitions 
from (5) with large residuals in all fits were omitted; see 
respective line file. Uncertainties of three out of four nu2 
data sets from (6) were increased slightly (by 0.00010 cm-1).

Additional data were taken from
(7) R. J. Saykally, P. G. Szanto, T. G. Anderson, and R. C. Woods, 
Astrophys. J. 204 (1976) L143;
(8) H. A. Bechtel, A. H. Steeves, and R. W. Field, 
Astrophys. J. 649 (2006) L53.