These determinate sentences eliminate extensive periods of probation or parole and attempt to ensure equivalent sentences for offenders who commit similar crimes and have similar criminal histories. Judges can depart from the guidelines under extenuating circumstances; prosecutors and defense counsel can appeal sentences outside the boundaries set by the standards. The chapter on sentencing guidelines explains the rules relating to offense seriousness level, offender score, standard sentence range, sentencing options, review of sentences, penalty and modification hearing, discharge and vacation of conviction record. The Sentencing Guidelines Commission also provides an index of commentary on the SRA. The third section consists of individual Offense Reference Sheets for all felonies with a standard sentencing range. They are arranged alphabetically with the exceptions of controlled substances, imitation controlled substances, and legend drug violations, which form a separate group. All crimes are indexed, along with a separate index for the drug-related crimes. Appendixes are the offense scoring forms, felony index, 1989 laws with delayed implementation dates, and classifications of felony offenses.