In 1928, I was working with the quantum mechanical calculations — which were very complicated mathematically — and I managed to derive the result that the carbon atom would form four bonds in tetrahedral directions, but it was so complicated that I thought, “People won’t believe it. It is so hard to see through this mass of symbols and equations and relationships that they won’t believe it. And perhaps I don’t believe it either!” It took a long time for me to simplify the quantum mechanical equations so that they were very easily applied to various problems. So around January 19, 1931, late in the day, I had this idea. I can use a simple method of simplifying a power method of simplifying these equations. Then I can apply these simplified equations to various chemical problems. So I worked nearly all night, very excited about applying this idea. I not only can easily derive the tetrahedral arrangement of the bonds of the carbon atoms, but also various other arrangement of atoms around a central atom, not only tetrahedral, but also octahedral ligation, and square planar ligation, which does occur with certain substances. And I did make predictions about relationships between magnetic properties and the arrangements of the atoms around each other. I considered that paper, which was published 17th of March, 1931, as my most important paper, and I believe I am right in saying that it is the one that developed the greatest feeling of excitement in me.