While Friedman often mentioned Hayek as an important influence, Hayek rarely mentioned Friedman. He deeply disagreed with Chicago School methodology, quantitative and macroeconomic focus, and claimed that Friedman's "Essays in Positive Economics" was as dangerous a book as Keynes' "General Theory". Friedman also claimed that despite some Popperian influence Hayek always retained basic Misesian praxeological view which he found "utterly nonsensical". He also noted that he admired Hayek only for his political works, and disagreed with his technical economics; he called "Prices and Production" a "very flawed book" and "The Pure Theory of Capital" "unreadable". There were occasional tensions at the Mont Pelerin meetings between the Hayek's and Friedman's followers that sometimes threatened to split the Society. Although they worked at the same university and shared political beliefs, Hayek and Friedman rarely collaborated professionally and were not close friends.