A new reference sheet is available in the Lesson Materials Section on Eb Tuning. This tuning, sometimes called 'Eb Standard', is when all six strings are tuned down a semitone. Many guitarists use this tuning so it's worth teaching your student how to change back and forth between Eb and Standard. The reference sheet contains all the essential information on the tuning as well as instructions on how to explain it.
There are reference sheets on other tunings under the TUN series in the Lesson Materials Section.