Although he never published this work in his lifetime, he developed many different approaches to the topic with many different notations being tried out to find the one which was most useful.
Kuigi ta ei avaldanud seda tööd oma eluajal, ta välja töötanud mitmeid erinevaid lähenemisi teema on palju erinevaid märked on katsetatud, et leida üks, mis oli kõige kasulikum.