9.2.5 Documents relating to the theory or principle behind the invention 

Where a document cited in the search report may be useful for a better understanding of the principle or theory behind the invention or shows that the reasoning or the facts behind it are incorrect, it is labelled with the letter "T".

In the latter case, the "T" document is evidence within the meaning of Art. 117(1)(c) rather than prior art within the meaning of Art. 54(2) and so it does not matter whether it was published before or after the searched application's priority or filing date.

For example: an applicant claims a group of chemical compounds and the description gives a generically defined process for their production. The search division finds a document published after the priority date which clearly shows that the generically defined process cannot produce all of the compounds covered by the claims. It can then cite it as a "T" document and use it to raise an Art. 84 objection that the claims are not supported by the description (see F‑IV, 6.3).