The Manolis Triantafyllidis Collection belongs to the Institute of Modern Greek Studies (Manolis Triantafyllidis Foundation)
and comprises of 2428 volumes, mainly on education and philosophy, including quite a few rare editions and manuscript works by Manolis Triantafyllidis himself. Most of this collection is digitized and part of it can be found here.
For additional information about this collection, you may visit this page (Greek text only!)
as well as the library website