共 50 条
- [21] HYPOELLIPTIC 2ND ORDER DIFFERENTIAL EQUATIONS ACTA MATHEMATICA UPPSALA, 1967, 119 (3-4): : 147 - &
- [27] Geometry of first integrals for 2nd order difference equations COMMUNICATIONS IN DIFFERENCE EQUATIONS, 2000, : 35 - 43
- [29] EXTENSION OF SOLUTIONS TO 2ND ORDER PARTIAL-DIFFERENTIAL EQUATIONS BY THE METHOD OF QUASIREVERSIBILITY HOUSTON JOURNAL OF MATHEMATICS, 1984, 10 (03): : 357 - 370