APA

International Gas Union I., . (2000). Actual development of the Gas Industry in Portugal. Portugal: International Gas Union.

Chicago

International Gas Union IGU, . 2000. Actual development of the Gas Industry in Portugal. Portugal: International Gas Union.

Harvard

International Gas Union I., . (2000). Actual development of the Gas Industry in Portugal. Portugal: International Gas Union.

MLA

International Gas Union IGU, . Actual development of the Gas Industry in Portugal. Portugal: International Gas Union. 2000.