Article: The two mature piano sonatas (No. 2, Op. 35, written in 1839 and No. 3, Op. 58, written in 1844) are in four movements. In Op. 35, Chopin was able to combine within a formal large musical structure many elements of his virtuosic piano technique—"a kind of dialogue between the public pianism of the brilliant style and the German sonata principle". The last movement, a brief (75-bar) perpetuum mobile in which the hands play in unmodified octave unison throughout, was found shocking and unmusical by contemporaries, including Schumann. The Op. 58 sonata is closer to the German tradition, including many passages of complex counterpoint, "worthy of Brahms" according to the music historians Kornel Michałowski and Jim Samson.

Question: What two people claimed that Op 58 was "worthy of Brahms"?
Kornel Michałowski and Jim Samson