[en] In the course of study of the K internal conversion coefficient of ⁹¹Y, reported in the previous volume of this annual report, αsub(K) and K/L+M+... ratio of ⁸⁷Sr were determined in the same way as those of ⁹¹Y from the peaks of 388 keV isomeric transition of ⁸⁷Sr presented in the γ-ray and electron spectra of ⁹¹Sr source, which had been measured by using a Ge(Li)-Si(Li) type internal conversion spectrometer. The obtained values were 0.18+-0.2 and 5.5+-0.9 for the αsub(K) and K/L+M+..., respectively, being good agreement with theoretical value for the M4 transition and the other experimental values. (auth.)