Não informado. Scientific information activities of federal agencies. U.S. National Science Foundation.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Scientific Information Activities of Federal Agencies. Washington: U.S. National Science Foundation.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Scientific Information Activities of Federal Agencies. U.S. National Science Foundation.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.