Pike, Roscoe "adhesive". Encyclopædia Britannica Online. Encyclopædia Britannica Inc..
doi.org
dx.doi.org
Mazza, P; Martini, F; Sala, B; Magi, M; Colombini, M; Giachi, G; Landucci, F; Lemorini, C et al. (January 2006). "A new Palaeolithic discovery: tar-hafted stone tools in a European Mid-Pleistocene bone-bearing bed". Journal of Archaeological Science33 (9): 1310. doi:10.1016/j.jas.2006.01.006.