Pode ser realmente "sem data" ou "nome (name)" seguido de "data":
Contributor Information and Titles
1) The main contributors of the source, normally the author, are placed before the title. If there is more than one author, arrange the authors in the same order found in the source. Use the first and middle name initials and the entire last name. Inverse all names before the title.
Eight or more Smith, J. K., Sampson, T., Hubbard, A. J., Anderson, J., Thompson, T., Silva, P.,… Bhatia, N. (Date). Title.
2) If there is no date, use “n.d” instead, which means “no date.”
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