**3.1. Research question**

**Figure 3.** Number of publications and papers cited in patents between 1998 and 2006.

**Figure 2.** Number of Japanese papers by sector in 1998–2006.

156 Scientometrics

Patent-paper citations are different from paper-paper citations in their statistic nature, such as their small amount compared to that of the latter. Therefore, some indicators developed in bibliometrics cannot be applied to patent-paper citations. To develop valid indicators, many aspects of their tendencies, especially which kind of papers were preferred to cite in patent, should be grasped. Although some studies tackled this question partially [4–6, 11], their analyses were restricted to the US patents [4, 5, 11] or limited numbers of "top" researchers [6].

Moreover, it is still unknown how papers were cited from patents of which feature values were relatively high (hereafter, they are called as high-feature-valued patents). Branstetter [12] addressed the question whether patents citing papers tended to be high feature valued. However, his approach was done from the patent side, not the paper side. Patent-paper citations from high-quality patents seemed to be more valuable from the view of possibility of occurrence of innovation in many cases.

Here, I tried to grasp statistical tendencies of relationship between patent-paper citations from both all patents and those with high feature values. I intended to show the difference between them and to obtain basic knowledge of paper citations from high-feature-valued patents to develop valid indicators and show tendencies of (Japanese) scientific research from multi-aspects of patent-paper citations in the following sections.
