O. N.  Dubovik, ?Krym'sko-Novorosiis'ki vydy rodu Hypericum L. (The Crimean-Novorosiisk species of the genus Hypericum L.)?, Ukr. Bot. Zhurn., vol. 38, pp. 8 - 12, 32 (1981) - map., 1981.

I.  Hagemann, ?Wuchsformenuntersuchungen an balkanischen Hypericum-Sippen. (Investigation of the growth form of Hypericum taxa from the Balkan Peninsula.)?, Bot. Jahrb., vol. 102, pp. 239 - 254 (1981) - illus., 1981.

D. E.  Culwell, ?Interspecific hybridization between Hypericum graveolens and H. mitchellianum.?, Castanea, vol. 46, pp. 323-333 (1981)- map., 1981.

J. M.  Gillett and Robson, N. K. B., The St. John's-wort of Canada (Guttiferae). Ottawa: National Museums of Canada, 1981, p. iv, 40p.- illus., maps, chrom. nos., keys.

C.  Reynaud, ?Contribution a L" etude cytotaxonomique du genre Hypericum I. en Turquie: 2.?, Ann. Univ. Provence, Biol. Ecol. Medit., vol. 8, pp. 181-191 (1981)- chrom. nos., 1981.

T. L.  Andrienko, Birchenko, V. M., and Didukh, Y. P., ?Pershi znakhidky Hypericum humifusum L. na Ukrayins'komu polissi. (First occurrences of Hypericum humifusum L. in Ukrainian Polessie.)?, Ukr. Bot. Zhurn., vol. 38, pp. 71 - 72 (1981) - map., 1981.

N. K. B.  Robson, ?Studies in the genus Hypericum L.  (Guttiferae).  2.  Characters of the genus.?, Bull. Brit. Mus. (Nat. Hist.), Bot., vol. 8, pp. 55-226, 1981.

N. K. B.  Robson, ?Hypericum specimens collected by Roy Lancaster in south-western China, October 1980.?, Int. Dendrol. Soc. Year Book, p. 141 (1980 publ. 1981) -, 1981.

N. K. B.  Robson, ?Studies in the genus Hypericum L. (Guttiferae): 2. Characters of the genus.?, Bull. Brit. Mus. (Nat. Hist.) Bot., vol. 8, pp. 55 - 226 (1981) - illus., chrom. nos., maps., 1981.