Context: On his mother's side, Hayek was second cousin to the philosopher Ludwig Wittgenstein. His mother often played with Wittgenstein's sisters, and had known Ludwig well. As a result of their family relationship, Hayek became one of the first to read Wittgenstein's Tractatus Logico-Philosophicus when the book was published in its original German edition in 1921. Although Hayek met Wittgenstein on only a few occasions, Hayek said that Wittgenstein's philosophy and methods of analysis had a profound influence on his own life and thought. In his later years, Hayek recalled a discussion of philosophy with Wittgenstein, when both were officers during World War I. After Wittgenstein's death, Hayek had intended to write a biography of Wittgenstein and worked on collecting family materials; and he later assisted biographers of Wittgenstein.

Question: Who was among the first readers of Ludwig  Wittgenstein's book?
Answer: Hayek

Question: How often times did Hayek and Wittgenstein meet?
Answer: on only a few occasions

Question: Whose philosophy heavily influenced Hayek?
Answer: Ludwig Wittgenstein

Question: What did Wittgenstein and Hayek do during the first world war?
Answer: both were officers

Question: What was the name of the book Wittgenstein published in 1921?
Answer: Wittgenstein's Tractatus Logico-Philosophicus