Cole returned to Harvard and wrote a thesis A Contribution to the Theory of the General Equation of the Sixth Degree which, as the title indicates, studied equations of degree 6.
Koul ibabalik sa Harvard at wrote isang sanaysay Isang kontribusyon sa teorya ng Pangkalahatang equation ng Sixth Degree na kung saan, bilang ang pamagat ay nagpapahiwatig, aral ng equation ng degree 6.