In 1997, statistically significant differences in the content of oil were found between the samples from England with 40.39 /0.23% and Finland (PEI) with 40.49 /0.22% on the lower level, and the samples from Denmark (BOR) with 44.09 / 0.64% and from Sweden with 43.79 /0.12% on the upper level. In 1998, the