Heliölä, J., Koivula, M., Niemelä, J. (2001): Distribution of carabid beetles (Coleoptera, Carabidae) across a boreal forest-clearcut ecotone. Conservation Biology, 15: 370-377.
Helliwell, D.R. (1973): The growth of sycamore (Acer pseudoplatanus L.) seedlings in different woodland soils. Grange-over-Sands, Nature Conservancy, 15pp. (Merlewood Research and Development Paper No.48)
Helliwell, D.R. (1974):The growth of sycamore (Acer pseudoplatanus L.) and birch (Betula verrucosa Ehrh.) seedlings in 50 different soils. Grange-over-Sands, Institute of Terrestrial Ecology, 13pp. (Merlewood Research and Development Paper No.58)