[18] Zie "A European Environmental Aviation Charge" van het Centrum voor energiebesparing en schone technologie, Delft, 1998 en het rapport "Emission Charges and Taxes in Aviation, Den Haag, 1998.
[18] Siehe -A European Environmental Aviation Charge", Centre for Energy Conservation and Environmental Technology, Delft 1998, und den Bericht -Emission Charges and Taxes in Aviation", Den Haag 1998