ɪn dɪˈɑːfɐntˌiːn ɐpɹˌɑːksɪmˈeɪʃən ænd ðə θˈiəɹi ʌv kwɑːdɹˈæɾɪk fˈɔːɹmz, hiː pɹəpˈoʊzd ðɪ ˈɑːpənhˌaɪm kəndʒˈɛktʃɚ.
In Diophantine approximation and the theory of quadratic forms, he proposed the Oppenheim conjecture.