Comparing Spectra
ETA, year
==================
ObsPer   DerPer
------------------
301      226  *
120      130  *
 90       90.2*
 69.4     69.4*
 54.7     56.4*
 47.5     46.3*
 34.7     34.7
 27.0     27.0
 23.4     24.0
 22.0     22.0
 15.3     15.3
 13.2     13.2
 11.1     11.1
  7.8      7.8
 (5.0)     5.0
 (4.7)     4.7
 (4.0)     4.0
 (3.5)     3.5
----------------------
(x.y) present but not
      labelled in the plots
* weak