The two quickly became friends and they would collaborate closely for many years. Hellinger left Göttingen in 1909, four years before Toeplitz, but before that the two were already producing joint papers.
Ang dalawang mabilis na naging kaibigan at sila ay malapit na magtulungan para sa maraming taon. Hellinger kaliwa Gottingen sa 1909, apat na taon bago Toeplitz, ngunit bago na ang dalawa ay na paggawa pinagsamang mga papeles.