Asterisk codecs - questions on g.726 and adpcm

after having:
core show codecs
on Asterisk 1.8 among a few lines of result I saw:
g726aal2 (G.726 AAL2)
adpcm (ADPCM)
g726 (G.726 RFC3551)

Actually, I though that g726 is simply G.711 with ADPCM as an additional method.
What are the differences between those codecs and what is here aspcm?

Thank you.


There is a nice description of G.726 here:

AAL2 packing is opposite order for samples into octets.