APA

Gibbs P. e., . (2006). Taxonomic studies on the genus Echium 1. An outline revision of the spanish species / P. E. Gibbs. : .

Chicago

Gibbs P e, . 2006. Taxonomic studies on the genus Echium 1. An outline revision of the spanish species / P. E. Gibbs. : .

Harvard

Gibbs P. e., . (2006). Taxonomic studies on the genus Echium 1. An outline revision of the spanish species / P. E. Gibbs. : .

MLA

Gibbs P e, . Taxonomic studies on the genus Echium 1. An outline revision of the spanish species / P. E. Gibbs. : . 2006.