The Term Fugitive Literature or Grey Literature Refers to Research

The term fugitive literature or grey literature refers to research reports

A) that exist in forms, such as technical reports, that are often not covered by the more commonly used indexes.
B) published in mainstream journals but are not often cited by other researchers.
C) published prior to the time that indexes to the research literature were established and so are difficult to locate.
D) that describe studies that appear to be low in internal validity.