APA (7th ed.) Citation

de Juan, S. G. (1991). The Guadalquivir marshes. Focus, 41(1), 6.

Chicago Style (17th ed.) Citation

de Juan, S. Garcia. "The Guadalquivir Marshes." Focus 41, no. 1 (1991): 6.

MLA (9th ed.) Citation

de Juan, S. Garcia. "The Guadalquivir Marshes." Focus, vol. 41, no. 1, 1991, p. 6.