Analysing European and International Patent Citations: A Set of EPO Patent Database Building Blocks
This paper presents a preliminary set of European and international citation data tables designed to enable researchers to become familiar with the subject and undertake a range of analyses. It addresses analytical and statistical issues such as why citations from international searches and European searches should be combined; the calculation of citation lags; use of International Patent Classification (IPC) codes for grouping patents according to technology; treatment of references to Non-Patent Literature; and the notion that many publications, from different patenting authorities, covering the same invention can be cited.
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http://lysander.sourceoecd.org/vl=3670275/cl=23/nw=1/rpsv/cgi-bin/wppdf?file=5lgl4dtfrm0n.pdf