1. 1) Japan TAPPI：“Recycled paper”, in “Dictionary of Pulp and Paper, the Revised Sixth Edition”, Japan TAPPI, Tokyo, p. 107 （2014）.
2. 2) Nomura, T.：“Recycled paper”, in “Printing Paper to be Used with Good Care”, Japan Printing News, Co., Ltd., Tokyo, p. 42-43 （1993）.
3. 3) Komiya, H.：“Paper began as recycled fiber”, in “A Comprehensive Book on Paper”, Nikkan Kogyo Shimbun Ltd., Tokyo, p. 72 （2001）.
4. 4) Hara, H.：“Wastepaper and recycled paper”, in “The Paper Story, the Revised Edition”, Japanese Standards Association, Tokyo, p. 136-149 （2002）.
5. 6) Paper Recycling Promotion Center：“Paper Recycling in Japan”, p. 5-6 （2022）, PAPER-RECYCLING-IN-JAPAN-English.pdf （prpc.or.jp）.