C. Bai and J. Fang, Existence of positive solutions for three-point boundary value problems at resonance, J. Math. Anal. Appl. 291 (2004), no. 2, 538--549.
Y. Chen and X. Tang, Positive solutions of fractional differential equations at resonance on the half-line, Bound. Value Probl. 2012 (2012), Article no. 64, 13 pages.
J. Chu and F. Wang, An order-type existence theorem and applications to periodic problems, Bound. Value Probl. 2013 (2013), Article no. 37, 12 pages.
C.T. Cremins, A fixed-point index and existence theorems for semilinear equations in cones, Nonlinear Anal. 46 (2001), no. 6, 789--806.
Y. Cui and J. Sun, Fixed point theorems for a class of nonlinear operators in Hilbert spaces with lattice structure and application, Fixed Point Theory Appl. 2013 (2013), Article no. 345, 9 pages.
Y. Cui and X. Zhang, Fixed points for discontinuous monotone operators, Fixed Point Theory Appl. 2010 (2010), Article ID 926209, 11 pages.
D. Franco, G. Infante and M. Zima, Second order nonlocal boundary value problems at resonance, Math. Nachr. 284 (2011), no. 7, 875--884.
X. Han, Positive solutions for a three-point boundary value problem at resonance, J. Math. Anal. Appl. 336 (2007), no. 1, 556--568.
G. Infante and M. Zima, Positive solutions of multi-point boundary value problems at resonance, Nonlinear Anal. 69 (2008), no. 8, 2458--2465.
S. Liang and L. Mu, Multiplicity of positive solutions for singular three-point boundary value problems at resonance, Nonlinear Anal. 71 (2009), no. 7-8, 2497--2505.
Y. Liu and C. Shen, On the existence of positive solution for a kind of multi-point boundary value problem at resonance, Nonlinear Anal. 72 (2010), no. 11, 4211--4220.
Y. Liu and C. Shen, Positive solutions for second order four-point boundary value problems at resonance, Topol. Methods Nonlinear Anal. 38 (2011), no. 1, 1--15.
J. Mawhin, Equivalence theorems for nonlinear operator equations and coincidence degree theory for some mappings in locally convex topological vector spaces, J. Differential Equations 12 (1972) 610--636.
D. O'Regan and M. Zima, Leggett-Williams norm-type theorems for coincidences, Arch. Math. (Basel) 87 (2006), no. 3, 233--244.
W.V. Petryshyn, Using degree theory for densely defined A-proper maps in the solvability of semilinear equations with unbounded and noninvertible linear part, Nonlinear Anal. 4 (1980), no. 2, 259--281.
A. Yang and W. Ge, Existence of positive solutions for self-adjoint boundary value problems with integral boundary conditions at resonance, Electron. J. Differential Equations 2011 (2011), no. 11, 8 pages.
A. Yang and H. Wang, Positive solutions of two-point boundary value problems of nonlinear fractional differential equation at resonance, Electron. J. Qual. Theory Differ. Equ. 2011 (2011), no. 71, 15 pages.
H. Zhang and J. Sun, Positive solutions of third-order nonlocal boundary value problems at resonance, Bound. Value Probl. 2012 (2012), Article ID 102, 10 pages.
M. Zima, Existence of positive solutions for a second-order three-point boundary value problem at resonance, in: Dynamic Systems and Applications, Vol. 5, pp. 527--532, Dynamic, Atlanta, GA, 2008.
M. Zima, Positive solutions for first-order boundary value problems at resonance, Commun. Appl. Anal. 13 (2009), no. 4, 671--680.
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