there is no learning scroll for concentation increase scrolls and does not show up on the scroll skills list, to my knowledge they can be obtained only from quests.
Also there are no learning scrolls for strength and quickness potions same as above and no learning scrolls for t5 decomp although the list of T5 decompable (is that a word?
) items does appear at 100000 decomp points.
T4 stone learning scrolls were implemented in the last download or so they said and they are on the skill list. I have yet to see one.