1. 1) Ministry of the Environment：“Basic Policy on Promoting Green Procurement （Provisional Translation）” （2022） 8-15, https://www.env.go.jp/en/laws/policy/green/h31bp_en.pdf
2. 2) Paper Recycling Promotion Center：“2021 Statistics of Recovered Paper in Japan （Final version）” （2022） 1-11, http://www.prpc.or.jp/wp-content/uploads/ 220401-2021-statistics-of-recovered-paper-in-Japan.pdf
3. 3) Ishikawa, K., Yamada, M. Ichikawa, C.：Paper and Pulp Technology, 47 （2）, 10-17 （1996）.
4. 4) Osada, T., Ichihara, K., T. Jikibara, T. Araki：Proc. the 1998 Pulp and Paper Research Conference, 2-5 （1998）.
5. 5) Osada, T., Ichihara, K.：A test method of identifying pulp fibers derived from wastepaper, and devices for determining the blending rate of wastepaper, Japan Patent Kokai Koho, Heisei 11-344445 （1999）