@book{ECDL_2,
author = "Σιδηρόπουλος, Νίκος and Χατζηγεωργίου, Νίκος",
publisher = "LibrisTech ΑΕ",
title = "{E}uropean {C}omputer {D}riving {L}icence (ECDL), {Ε}νότητα {A}M4: {Λ}ογιστικά Φύλλα, {Π}ροχωρημένο {Ε}πίπεδο ",
year = "2004",
}