We have used our unbiased 4-fit method to analyze the high-temperature series of Butera, Comi, and Marchesini [Phys. Rev. B 40, 534 (1989)]. Our results are consistent with theirs. However, our method of analysis has the advantage that it is tailored to detect either a power-law singularity or a singularity like that predicted by Kosterlitz and Thouless, in that the value of one of the parameters determined in our 4-fit procedure signals which type of singularity is dominant. Therefore, our method provides a quantitative indicator of the dominant type of singularity. Our results unambiguously support Kosterlitz-Thouless predictions over power-law forms for the singularities.

• Received 15 February 1990

DOI:https://doi.org/10.1103/PhysRevB.42.10769