Q. Dear CMOS, Would you please add guidance about how to cite a nonrecoverable source—i.e., a work that cannot be accessed or retrieved by a reader. For example, I was editing a conference paper that had this in the references list: eTerrestrial: an online Portal for terrestrial services, https://www.itu.int/ITU-R/eTerrestrial/eMIFR. Clicking on the eMIFR link in the conference paper brings up a web page that requires users to sign in. Because the tools in the eTerrestrial portal are inaccessible to everybody but members of the International Telecommunication Union, how should this source be cited?
A. In Chicago and other styles, source citations don’t generally require info about how to access the cited sources. For example, when you cite an article in an academic journal, you don’t need to clarify that readers may need a subscription or library access to read the article (or that they may need to pay a fee to get it).
This approach is necessary because access to most sources is limited in some way (sources don’t magically appear for anyone) and because any restrictions are subject to change without notice.
That said, there’s no rule against including such info in special cases. Here’s how we might add such information to your example, which we’ve adapted here for use with Chicago’s author-date system:
ITU (International Telecommunication Union). n.d. eMIFR (Master International Frequency Register tool). eTerrestrial: An Online Portal for Terrestrial Services. Accessed September 9, 2025. https://www.itu.int/ITU-R/eTerrestrial/eMIFR (requires a TIES [Telecommunication Information Exchange Services] account).
For the use of n.d. (no date) in author-date citations, see CMOS 14.104. For the use of abbreviations in author-date style for an organization as author, see 13.127.