Some Recent Publications
 Minimization problems for noncoercive functionals subject to
constraints (with V. K. Le), I. Trans. Amer. Math. Soc. 347(1995),
44854513. II. Adv. Diff. Equations 1(1996), 453498.
 Positive solutions of semilinear elliptic equations, pp. 447500 in
Topological Methods in Differential Equations, Kluwer, Boston, 1995.
 On the principal eigenvalue of pLaplacian like operators (with
M. GarciaHuidobro and R. Manasevich), J. Diff. Equations 130(1996),
235246.
 Global Bifurcation in Variational Inequalities: Applications to
Obstacle and Unilateral Problems (with V. K. Le),
Springer Verlag, New York, 1997.

On Neumann problems for semilinear elliptic equations with critical
nonlinearity: existence and symmetry of multipeaked solutions
(with S. MaierPaape and Z. Q. Wang),
Comm. PDE 22(1997), 14931527.

On boundary value problems for degenerate quasilinear elliptic
equations and inequalities (with V. K. Le), J. Differential Equations
144(1998), 170218.

Positive radial solutions of quasilinear elliptic partial differential
equations on a ball (with M. GarciaHuidobro,
and R. Manasevich). Nonlinear Analysis 35(1999), 175190.

On boundary value problems for quasilinear elliptic equations,
Fields Institute Communications 21(1999), 419427.

On principal eigenvalues for quasilinear elliptic differential
operators:
An OrliczSobolev space setting (with M. GarciaHuidobro, V. Le,
and R. Manasevich). Nonl. Diff. Equations and Applications 6(1999),
207225.

Solutions of mountain pass type of quasilinear elliptic equations
(with P. Clement, M. GarciaHuidobro, and R. Manasevich).
Calculus of Variations and PDE 11(2000), 3362.

On Critical points for noncoercive functionals and subharmonic
solutions of some nonlinear Hamiltonian systems (with Z. Wang),
Electr. J. Diff. Equations, 2000, 237245.

On the existence of soliton solutions of quasilinear Schroedinger
equations
(with M. Poppenberg and Z. Wang), Calculus of Variations and PDE,
14(2002),
329344.

Quasilinear elliptic equations and inequalities with rapidly
growing coefficients (with V. K. Le), Journal London Math. Soc.
62(2000), 852872.

Variational inequalities, bifurcation and
applications. Nonlinear Analysis and its Applications to Differential
Equations.
Pages 113143 in Progr. Nonlinear Differential Equations Appl., 43, Birkhäuser,
Boston, 2001.

On the existence of nontrivial solutions to some elliptic
variational inequalities (with V. Le), Advanced Nonlinear Studies,
2(2002), 251262.

The LiouvilleBratuGelfand problem for radial operators (with
J. Jacobsen),
Journal of Differential Equations, 184(2002), 283298.

Radial solutions of quasilinear elliptic differential equations (with
J. Jacobsen),
pp. 359436 in Handbook of Differential Equations, ed. by Canada,
Drabek, Fonda; Elsevier, 2004.

Variational methods for nonlinear eigenvalue inequalities
(with An Le and Vy Le), Vietnamese J. Math. 32(2004), 4348.

Periodic solutions of second order equations 
a variational approach, pp. 213220 in The First Sixty Years of
Nonlinear Analysis of Jean Mawhin, edited by M. Delgado,
J. L{\'o}pezG{\'o}mez, R. Ortega, and A. Su{\'a}rez, World
Scientific, Singapore, 2004.

Bifurcation problems associated with generalized
Laplacians
(with Inbo Sim), Advances in Differential Equations 9(2004), 797828.

On generalized and viscosity solutions of nonlinear
elliptic equations (with D. Hartenstine), Advanced Nonlinear Studies
4(2004), 289306.

AmbrosettiProdi type problems for quasilinear
elliptic equations (with Eiko Koizumi), Differential and Integral
Equations, 18(2005), 241262.

Subsupersolution theorems for quasilinear elliptic
problems: A variational approach (with V. Le),
Elect. J. Diff. Equations 2004(2004), 118, 17.

Some general concepts of sub and supersolutions for
nonlinear elliptic problems (with V. Le),
Top. Meth. Nonl. Anal. 28(2006),
87103.

Variational eigenvalues of degenerate eigenvalue problems for the
weighted pLaplacian (with An Le), Advanced Nonlinear Studies
5(2005), 553565.

On positive solutions of quasilinear elliptic equations
(with N. Loc), Differential and Integral Equations 22(2009), 829842.

The Contraction Mapping Principle and Some
Applications
(with R. Brooks), Electr. J. Diff. Equations Monograph 09, 2009.
ISSN 10726691.

Equations and inequalities in OrliczSobolev spaces: Selected topics
(with V. K. Le), pp. 295351 in Handbook on Nonconvex Analysis and
Applications, D. Motreanu, editor,
International Press, 2010.

Boundary value problems for singular elliptic problems (with N. Loc),
Rocky Mtn. J. Math. 41(2011), 555572.

On second order quadratic systems and algebras (with A. Sagle),
Differential and Integral Equations 24(2011), 877894.

Fixed set theorems, discrete dynamics and nonlinear boundary value
problems
(with R. Brooks and B. Warner), Elect. J. Diff. Equations 2011(2011),
no. 56, pp. 115.

Applications of subsupersolution theorems to singular elliptic
problems
(with N. Loc), Advanced Nonlinear Studies 11(2011), 493524.