Puukko, K. 1981. Okakaarnakuoriaisen, Ips acuminatus Gyll. (Coleoptera, Scolytidae) levinneisyyden nykyinen etelaraja Suomessa [The southern border of the present distribution on Ips acuminatus Gyll. (Coleoptera, Scolytidae) in Finnland]. Silva Fennica 15(2):222-227.