Beltran, D. G. (1973). A method of determining economical sample size for sample surveys [microform]. Photoduplication Service.
Lua i Stíl Chicago (17ú heag.)Beltran, Disodado G. A Method of Determining Economical Sample Size for Sample Surveys [microform]. Quezon City: Photoduplication Service, 1973.
Lua MLA (9ú heag.)Beltran, Disodado G. A Method of Determining Economical Sample Size for Sample Surveys [microform]. Photoduplication Service, 1973.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.