qnli question: During his attendance to von Mises' seminars, who did Hayek become friends with? sentence: It was sometime after reading Socialism that Hayek began attending von Mises' private seminars, joining several of his university friends, including Fritz Machlup, Alfred Schutz, Felix Kaufmann, and Gottfried Haberler, who were also participating in Hayek's own, more general, private seminar.