Optical diagnostics: accretion rates.

• The data. Disk Accretion Rates for T Tauri Stars
  Gullbring et al.
  http://adsabs.harvard.edu/abs/1998ApJ...492..323G

• The interpretation. Accretion and the Evolutiion of T Tauri Disks Hartmann, Lee, et al.
  http://adsabs.harvard.edu/cgi-bin/bib_query?1998ApJ...495..385H