COUNTEREXAMPLE TO A CONJECTURE OF HOPF,H.

[1] Aleksandrov A.D., 1958, VESTNIK LENINGRAD U, V13, P5

[2] ALEXANDROV AD, AM MATH SOC T 2, V21, P412

[3] COURANT R, 1962, METHODS MATH PHYSICS, V2

[4] do Carmo M, 2016, DIFFERENTIAL GEOMETR

[5] Eisenhart L.P., 1909, TREATISE DIFFERENTIA

[6] Garabedian P.R., 1964, PARTIAL DIFFERENTIAL

[7] SYMMETRY AND RELATED PROPERTIES VIA THE MAXIMUM PRINCIPLE [J]. COMMUNICATIONS IN MATHEMATICAL PHYSICS, 1979, 68 (03) : 209 - 243

[8] GILBARG D, 1983, ELLIPTIC PARTIAL DIF

[9] HOPF H, 1983, LECTURE NOTES MATH, V1000

[10] HSIANG WY, 1982, J DIFFER GEOM, V17, P337

[1] Aleksandrov A.D., 1958, VESTNIK LENINGRAD U, V13, P5

[2] ALEXANDROV AD, AM MATH SOC T 2, V21, P412

[3] COURANT R, 1962, METHODS MATH PHYSICS, V2

[4] do Carmo M, 2016, DIFFERENTIAL GEOMETR

[5] Eisenhart L.P., 1909, TREATISE DIFFERENTIA

[6] Garabedian P.R., 1964, PARTIAL DIFFERENTIAL

[7] SYMMETRY AND RELATED PROPERTIES VIA THE MAXIMUM PRINCIPLE [J]. COMMUNICATIONS IN MATHEMATICAL PHYSICS, 1979, 68 (03) : 209 - 243

[8] GILBARG D, 1983, ELLIPTIC PARTIAL DIF

[9] HOPF H, 1983, LECTURE NOTES MATH, V1000

[10] HSIANG WY, 1982, J DIFFER GEOM, V17, P337