It was a topic which Eilenberg had been interested in from 1966 onwards and it is worth noting that it is one of the few major works by Eilenberg which he worked on alone.
Ito ay isang paksa na Eilenberg had been interesado sa mula sa 1966 pasulong at ito ay nagkakahalaga ng pagpuna na ito ay isa sa mga ilang pangunahing gumagana sa pamamagitan ng Eilenberg na kung saan siya nagtrabaho sa nag-iisa.