• [1] John H. Barrett, Fourth order boundary value problems and comparison theorems, Canad. J. Math. 13 (1961), 625–638. MR 0133519 (24 #A3350)
• [2] Earl A. Coddington and Norman Levinson, Theory of ordinary differential equations, McGraw-Hill Book Company, Inc., New York-Toronto-London, 1955. MR 0069338 (16,1022b)
• [3] Philip Hartman, Ordinary differential equations, John Wiley & Sons Inc., New York, 1964. MR 0171038 (30 #1270)
• [4] Philip Hartman and Aurel Wintner, On disconjugate differential systems, Canad. J. Math. 8 (1956), 72–81. MR 0074595 (17,611h)
• [5] Robert W. Hunt, The behavior of solutions of ordinary, self-adjoint differential equations of arbitrary even order, Pacific J. Math. 12 (1962), 945–961. MR 0147725 (26 #5239)
• [6] Robert W. Hunt, Oscillation properties of even-order linear differential equations, Trans. Amer. Math. Soc. 115 (1965), 54–61. MR 0203132 (34 #2985), http://dx.doi.org/10.1090/S0002-9947-1965-0203132-X
• [7] W. J. Kim, Disconjugacy and disfocality of differential systems, J. Math. Anal. Appl. 26 (1969), 9–19. MR 0236464 (38 #4759)
• [8] Walter Leighton and Zeev Nehari, On the oscillation of solutions of self-adjoint linear differential equations of the fourth order, Trans. Amer. Math. Soc. 89 (1958), 325–377. MR 0102639 (21 #1429), http://dx.doi.org/10.1090/S0002-9947-1958-0102639-X
• [9] A. Ju. Levin, Some questions on the oscillation of solutions of linear differential equations, Dokl. Akad. Nauk SSSR 148 (1963), 512–515 (Russian). MR 0146450 (26 #3972)
• [10] A. Ju. Levin, On the distribution of zeros of solutions of a linear differential equation, Dokl. Akad. Nauk SSSR 156 (1964), 1281–1284 (Russian). MR 0164079 (29 #1378)
• [11] David London and Binyamin Schwarz, Disconjugacy of complex differential systems and equations, Trans. amer. Math. Soc. 135 (1969), 487–505. MR 0237875 (38 #6154), http://dx.doi.org/10.1090/S0002-9947-1969-0237875-2
• [12] Zeev Nehari, On an inequality of Lyapunov, Studies in mathematical analysis and related topics, Stanford Univ. Press, Stanford, Calif., 1962, pp. 256–261. MR 0145149 (26 #2684)
• [13] Zeev Nehari, Disconjugate linear differential operators, Trans. Amer. Math. Soc. 129 (1967), 500–516. MR 0219781 (36 #2860), http://dx.doi.org/10.1090/S0002-9947-1967-0219781-0
• [14] William T. Reid, Principal solutions of non-oscillatory self-adjoint linear differential systems, Pacific J. Math. 8 (1958), 147–169. MR 0098220 (20 #4682)
• [15] William T. Reid, Oscillation criteria for self-adjoint differential systems, Trans. Amer. Math. Soc. 101 (1961), 91–106. MR 0133518 (24 #A3349), http://dx.doi.org/10.1090/S0002-9947-1961-0133518-X
• [16] Binyamin Schwarz, Disconjugacy of complex differential systems, Trans. Amer. Math. Soc. 125 (1966), 482–496. MR 0206371 (34 #6190), http://dx.doi.org/10.1090/S0002-9947-1966-0206371-8
• [17] Thomas L. Sherman, Properties of solutions of 𝑛𝑡ℎ order linear differential equations, Pacific J. Math. 15 (1965), 1045–1060. MR 0185185 (32 #2654)
• [18] T. L. Sherman, Properties of solutions of quasi-differential equations, Duke Math. J. 32 (1965), 297–304. MR 0179411 (31 #3659)
• [19] Robert L. Sternberg, Variational methods and non-oscillation theorems for systems of differential equations, Duke Math. J. 19 (1952), 311–322. MR 0048668 (14,50c)
• [20] H. M. Sternberg and R. L. Sternberg, A two-point boundary problem for ordinary self-adjoint differential equations of fourth order, Canadian J. Math. 6 (1954), 416–419. MR 0061738 (15,874c)
• [21] Aurel Wintner, On the non-existence of conjugate points, Amer. J. Math. 73 (1951), 368–380. MR 0042005 (13,37d)

Bibliography

[1]

J. H. Barrett, Fourth order boundary value problems and comparison theorems, Canad. J. Math. 13 (1961), 625-638. MR 0133519 (24:A3350)

[2]

E. A. Coddington and N. Levinson, Theory of ordinary differential equations, McGraw-Hill, New York, 1955. MR 0069338 (16:1022b)

[3]

P. Hartman, Ordinary differential equations, Wiley, New York, 1964. MR 0171038 (30:1270)

[4]

P. Hartman and A. Wintner, On disconjugate differential systems, Canad. J. Math. 8 (1956), 72-81. MR 0074595 (17:611h)

[5]

R. W. Hunt, The behavior of solutions of ordinary, self-adjoint differential equations of arbitrary even order, Pacific J. Math. 12 (1962), 945-961. MR 0147725 (26:5239)

[6]

-, Oscillation properties of even-order linear differential equations, Trans. Amer. Math. Soc. 115 (1965), 54-61. MR 0203132 (34:2985)

[7]

W. J. Kim, Disconjugacy and disfocality of differential systems, J. Math. Anal. Appl. (to appear). MR 0236464 (38:4759)

[8]

W. Leighton and Z. Nehari, On the oscillation of solutions of self-adjoint linear differential equations of the fourth order, Trans. Amer. Math. Soc. 89 (1958), 325-377. MR 0102639 (21:1429)

[9]

A. Ju. Levin, Some questions on the oscillation of solutions of linear differential equations, Dokl. Akad. Nauk SSSR 148 (1963), 512-515 = Soviet Math. Dokl. 4 (1963), 121-124. MR 0146450 (26:3972)

[10]

-, Distribution of the zeros of solutions of a linear differential equation, Dokl. Akad. Nauk SSSR 156 (1964), 1281-1284=Soviet Math. Dokl. 5 (1964), 818-821. MR 0164079 (29:1378)

[11]

D. London and B. Schwarz, Disconjugacy of complex differential systems and equations, Trans. Amer. Math. Soc. 135 (1969), 487-505. MR 0237875 (38:6154)

[12]

Z. Nehari, On an inequality of Lyapunov, Studies in mathematical analysis and related topics, pp. 256-261, Stanford Univ. Press, Stanford, California, 1962. MR 0145149 (26:2684)

[13]

-, Disconjugate linear differential operators, Trans. Amer. Math. Soc. 129 (1967), 500-516. MR 0219781 (36:2860)

[14]

W. T. Reid, Principal solutions of non-oscillatory self-adjoint linear differential equations, Pacific J. Math. 8 (1958), 147-169. MR 0098220 (20:4682)

[15]

-, Oscillation criteria for self-adjoint differential systems, Trans. Amer. Math. Soc. 101 (1961), 91-106. MR 0133518 (24:A3349)

[16]

B. Schwarz, Disconjugacy of complex differential systems, Trans. Amer. Math. Soc. 125 (1966), 482-496. MR 0206371 (34:6190)

[17]

T. L. Sherman, Properties of solutions of nth order linear differential equations, Pacific J. Math. 15 (1965), 1045-1060. MR 0185185 (32:2654)

[18]

-, Properties of solutions of quasi-differential equations, Duke Math. J. 32 (1965), 297-304. MR 0179411 (31:3659)

[19]

R. L. Sternberg, Variational methods and non-oscillation theorems for systems of differential equations, Duke Math. J. 19 (1952), 311-322. MR 0048668 (14:50c)

[20]

H. M. Sternberg and R. L. Sternberg, A two-point boundary problem for ordinary self-adjoint differential equations of fourth order, Canad. J. Math. 6 (1954), 416-419. MR 0061738 (15:874c)

[21]

A. Wintner, On the non-existence of conjugate points, Amer. J. Math. 73 (1951), 368-380. MR 0042005 (13:37d)