Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates


    • 7 Accesses

    This is a preview of subscription content, log in to check access.

    Rights and permissions

    Reprints and Permissions

    About this article

    Cite this article

    Cronica. Trab. Estad. Invest. Oper. 18, 173–180 (1967). https://doi.org/10.1007/BF03001709

    Download citation