hiː wɛnt ˌɔn tə dɪvˈɛləp ɐ θˈiəɹi ʌv dˈʌbəlvˈæljuːd fˈɔːɹməl ɡɹˈuːps ðæt lˈɛd tə ðə kˌælkjʊlˈeɪʃən ʌv kˈɑːboːɹdˌɪzəm ɹˈɪŋz ʌv kˈɑːmplɛks mˈænɪfˌoʊldz hˌævɪŋ sɪmplˈɛktɪk kˈʌvɚɹɪŋz ænd tə ðɪ ɛksplˈɪsɪt kənstɹˈʌkʃən ʌv wʌt ɑːɹ nˈaʊ nˈoʊn æz bˈʌtʃsteɪbɚ mˈænɪfˌoʊldz.
He went on to develop a theory of double-valued formal groups that led to the calculation of cobordism rings of complex manifolds having symplectic coverings and to the explicit construction of what are now known as  Buchstaber manifolds.