Eskola, S., Lauhikari, M., Voipio, H.-M. and Nevalainen, T. 1999. The use of aspen blocks and tubes to enrich the cage environment of laboratory rats. Scandinavian Journal of Laboratory Animal Science. 26, 1 (Dec. 1999). DOI:https://doi.org/10.23675/sjlas.v26i1.836.