APA

Kohler H., Billari F. C. & Ortega J. a.The emergence of lowest-low fertility in Europe during the 1990s. : .

Chicago

Kohler H.-P, Billari F C and Ortega J a.The emergence of lowest-low fertility in Europe during the 1990s. : .

Harvard

Kohler H., Billari F. C. and Ortega J. a.The emergence of lowest-low fertility in Europe during the 1990s. : .

MLA

Kohler H.-P, Billari F C and Ortega J a.: . .