1. Dennis, B. & Á. Helgadóttir, 1988. Breeding herbage species for northern Scandinavia. In: Natural Variation and Breeding for Adaptation, pp. 169–177. Proceedings of the Eucarpia Fodder Crops Section Meeting, Lusignan, France.
2. Helgadóttir, Á., 1989. Breeding herbage species for northern areas. 1. Variety trials with timothy (Phleum pratense L.). Acta Agric. Scand. 39: 243–254.
3. Hill, J., 1975. Genotype-environment interactions — a challenge for plant breeding. J. Agric. Sci. Camb. 85: 477–493.
4. Larsen, A., 1987. Gras-stripebakteriose i timoteikloner. Informasjonsmøte i plantevern 1987. SFFL Nr. 4: 153–158.
5. Lazenby, A. & H.H. Rogers, 1960. The evaluation of selection indices for yield in grass breeding. Proceedings of the 8th International Grassland Congress, Reading.