The tradition in this Israelian university is for visitors not to own their own office or to be gathered in a guests office, but to be welcomed by a permanent professor to share his office. It has not only the benefit to immerse the guest in the mathematical life of the research institute, but also to quickly provoke mathematical exchanges and questions.

Upon my arrival, I discovered that it had been decided to share Joseph B.’s office - a very famous and impressive mathematician, especially for a young mathematician like I then was. It then has been kind of a (false) relief to discover that he was finally away during the time of my stay. But still. In B.’s office remains something of B.’s, something which testifies of his mathematical life and interests. I was finally welcomed by B.’s mathematical library.

I first noticed one or two very familiar and very specific books of my field - that is always very surprising - which seemingly have been opened many times as could be deduced from to the state of the broken binding’s covers. I then broadened my view to discover unknown but attracting books on other topics, topics I knew - while not how - were related to my own questions and interests.

My first day ended by 3 piles of books on my desk - one pile, one topic. My stay ended with a new question at the crossing of these three, a question which is now at the center of my daily research.