what does [citation] mean in google scholar search results? What does [citation] mean in Google scholar search results and why is it not clickable? I know there is also an option to include citations but I am not sure what that means? If something is cited is should exist somewhere.

example: 


  [CITATION] Use of detergents in the analysis of fibrous feeds. IV.
  Determination of plant cell-wall constituents PJ Van Soest, RH Wine -
  J. Assoc. Off. Anal. Chem, 1967
[Citation] means that Google Scholar has not been able to find a source for the publication, but that it has inferred that it exists because other publications cite it.

Taken directly from Google Scholar help
"These are articles which other scholarly articles have referred to, but which we haven't found online. To exclude them from your search results, uncheck the "include citations" box on the left sidebar."