Häring A.M., Dabbert S., Aurbacher J., Bichler B., Eichert C., Gambelli D., Lampkin N., Offermann F., Olmos S., Tuson J., Zanoli R. (2004). Impact of CAP measures on environmentally friendly farming systems. Status quo, analysis and recommendations: The case of organic farming. Bruxelles (Belgique) : Commission Européenne. 205 p.