(C) 2000 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint. Printed in Singapore. J. oflnequal. & Appl., 2000, Vol. 5, pp. 381-395 Reprints available directly from the publisher Photocopying permitted by license only Perturbed Iterative Algorithms with Errors for Completely Generalized Strongly Nonlinear Implicit Quasivariational Inclusions S.H. SHIM a, S.M. KANG a, N.J. HUANG b and Y.J. CHO a,. a Department of Mathematics, Gyeongsang National University, Chinju 660-701, South Korea; b Department of Mathematics, Sichuan University, Chengdu, Sichuan 610064, RR. China (Received 4 May 1999; Revised 27 July 1999) In this paper, we introduce a new class of completely generalized strongly nonlinear implicit quasivariational inclusions and prove its equivalence with a class of fixed point problems by using some properties of maximal monotone mappings. We also prove the existence of solutions for the completely generalized strongly nonlinear implicit quasivariational inclusions and the convergence of iterative sequences generated by the perturbed algorithms with errors. Keywords: Completely generalized strongly nonlinear implicit quasivariational inclusion; Mann type iterative sequence with errors; Ishikawa type iterative sequence with errors 1991 Mathematics Subject 1 Classification: 49J40, 47H06 INTRODUCTION It is well known that variational inequality theory and complementarity problem theory are very powerful tool of the current mathematical technology. In recent years, classical variational inequality and complementarity problem have been extended and generalized to study a * Corresponding author. 381 S.H. SHIM et al. 382 wide class of problems arising in mechanics, physics, optimization and control, nonlinear programming, economics and transportation equilibrium and engineering sciences, etc. Various quasi-(implicit)variational inequalities, generalized quasi-(implicit)variational inequalities, quasi(implicit)complementarity problem and generalized quasi-(implicit)complementarity problem are very important generalizations of these classical problems. For details we refer to [1,3-18,20-29] and the references therein. Recently, Huang [15,16] introduced and studied the Mann and Ishikawa type perturbed iterative sequences with errors for the generalized implicit quasivariational inequalities and inclusions. Inspired and motivated by recent research works in this field, in this paper, we introduce a new class of completely generalized strongly nonlinear implicit quasivariational inclusions and prove its equivalence with a class of fixed point problems by using some properties of maximal monotone mappings. We also show the existence of solutions for this completely generalized strongly nonlinear implicit quasivariational inclusions and the convergence of iterative sequences generated by the perturbed algorithms with errors. 2 PRELIMINARIES Let H be a real Hilbert space endowed with a norm [l" and an inner product (.,.}. Letf, p, g, rn H H and N: H x H H be single-valued mappings. Suppose that M" H x H 2z is a set-valued mapping such that, for each fixed y E H, M(., y) H 2 n is a maximal monotone mapping and Range(g m) fq dom(M(., y)) :/: for each y E H. We consider the following problem: Find u H such that 0 - (g- m)(u)fq dom(M(., u)) 0, N(f(u),p(u)) + M((g- m)(u), u), where g- m is defined as (g- m)(u) g(u) (2.1) re(u) for each u E H. The problem (2.1) is called the completely generalized strongly nonlinear implicit quasivariational inclusion. NONLINEAR IMPLICIT QUASIVARIATIONAL INCLUSIONS 383 Now, we give some special cases of the problem (2.1) as follows: (I) If M(., y) 0qo(., y) for each y H, where p H x H R U { +oe} such that for each fixed y H, (., y) H R t3 {+oc} is a proper convex lower semicontinuous function on H and Range(g-m) for each y H and 0(., y) denotes the subdifferendom(0(., y)) tial of function (., y), then the problem (2.1) is equivalent to finding u H such that (g m)(u) dom(0(., u)) (U(f (u), p(u) ), v (g m)(u)) >_ p( (g m)(u), u) q(v, u) (2.2) for all v E H, which is called the generalized strongly nonlinear implicit quasivariational inclusion. (II) If N(u, v) u v for all u, v E H, then the problem (2.1) is equivalent to finding u H such that (g m)(u) f) dom(M(., u)) q), 0 f(u) p(u) + M((g m)(u), u), (2.3) which is called the generalized nonlinear implicit quasivariational inclusion, which was considered by Huang [16]. (III) If N(u, v) u v for all u, v H, m 0 and M(x, y) M(x) for all y H, where M: H 2z-/is a maximal monotone mapping, then the problem (2.1) is equivalent to finding u E H such that : g(u) fq dom(M(u)) O, 0 e f(u) -p(u) + M(g(u)), (2.4) which was studied by Adly [1]. (IV) If N(u, v) u v for all u, v E H and M(., y) 0(., y) for each yEH, where :HxHRt_J{+oc} such that, for each fixed yEH, o(., y):H R t_l {+oc} is a proper convex lower semicontinuous function on H and Range(g m) N dom(0o(., y)) 13 for each y E H and 0(., y) denotes the subdifferential of function o(., y), then the problem (2.1) is equivalent to finding u E H such that - (g m)(u) f3 dom(0qo(., u)) I, (f(u) -p(u), v (g- m)(u)) > qo((g- m)(u), u) p(v, u) (2.5) S.H. SHIM et al. 384 for all v E H, which is called the generalized quasivariational inclusion, which was considered by Ding [10]. (V) If N(u, v) u v for all u, v E H and M(., y) 0 for all y H, where 0 denotes the subdifferential of a proper convex lower semicontinuous function :H RU {+c}, then the problem (2.1) is equivalent to finding u H such that , (g- m)(u) f3 dom(0) :/: (f(u) -p(u), v (g- m)(u)) >_ p((g- m)(u)) (v) (2.6) for all v E H, which was studied by Kazmi [18]. (VI) If K:H 2H is a set-valued mapping such that, for each x E H, K(x) is a closed convex subset of H and, for each fixed y E H, M(., y) Oqo(., y), qo(., y) Ii(y)(.) is the indicator function of K( y) defined by IK(y) if x K( y), +, ifxK(y), j’ 0, then the problem (2.1) is equivalent to finding u H such that g(u) m(u) K(u), (N(f(u),p(u)), v (g- m)(u)) >_ O, (2.7) for all v K(u). It is clear that the completely generalized strongly nonlinear implicit quasivariational inclusion problem (2.1) includes many kinds of variational inequalities, quasivariational inequalities, complementarity problems and quasi-(implicit)complementarity problems of [1,6,1316,25-27] as special cases. PERTURBED ITERATIVE ALGORITHMS 3 LEMMA 3.1 u H is a solution of the problem (2.1)/f and only if there H such that exists u u F(u) def u (g m)(u) + jy(.,u)((g_ m)(u) aN(f(u),p(u))), (3.1) where a >0 is a constant and proximal mapping on H. J("u)(I+ aM(.,u)) -1 is the so-called NONLINEAR IMPLICIT QUASIVARIATIONAL INCLUSIONS 385 Proof Let u E H be a solution of the problem (3.1). From the definition of the proximal mapping j(.,u), it follows that (g- m)(u) aN(f(u),p(u)) (g- m)(u) + aM((g- m)(u), u) and so N(p(u),f (u)) e M((g m)(u), u). - Thus u H is a solution of the problem (2.1). Conversely, if u H is a solution of (2.1), we have u H such that (g m)(u) fq dom(M(., u)) and 0 N(f(u),p(u)) + M((g- m)(u), u). Hence we have (g- m)(u) 0 aN(f(u),p(u)) e (g- m)(u) + aM((g m)(u), u). From the definition of the proximal mapping jff(.,u), we know that u E H is a solution of the problem (3.1). This completes the proof. Based on Lemma 3.1, we now suggest and analyze the following new general and unified algorithms for the problem (2.1). (A) Mann Type Perturbed Iterative Algorithm with Errors (MTPIAE) H be mappings. Given u0 H, the iterative sequence {un} are defined by Let f,p, g, m H Un+l H and N: H x H "Tn)Un + OZn[Un (g- m)(Un) + j"(.,u,)((g m)(un) aN(f(un),p(un)))] + nen (1 On (3.2) for n=0, 1,2,..., where M n" H x H 2 / is a set-valued mapping such that, for each y H, M"(.,y):H 2n is a maximal monotone mapping for n=0, 1,2,..., a > 0 is a constant, {en} is a bounded S.H. SHIM 386 et al. sequence of the element of H introduced to take into account possible inexact computation and the sequences {an}, {Tn} in [0, 1] satisfying the following conditions: (1) an+Tn_< forn=0,1,2,..., (2) (3) En=oOZn 00, -_n=O’)/’n < 00. (B) Ishikawa Type Perturbed Iterative Algorithm with Errors (ITPIAE) H be mappings. Given u0 E H, the iterative sequence {un} are defined by H and N: H x H Let f,p, g, m H Un+l (1 an ")’n)Un -+- OZn[ln - (g m)(Vn) + j"(.,v,)((g_ m)(Vn) oN(f(Vn),P(Vn)))] +")’nen, n (1 /n n)bln /n[l’ln (g m)(Un) + .j"(.,u,)((g m)(Un) aN(f(un),p(un)))] + Snfn (3.3) for n 0, 1,2,..., where M n H x H 2 H is a set-valued mapping such that, for each y H, Mn(.,y):H 2 /is a maximal monotone mapping for n =0, 1,2,..., a > 0 is a constant, {en}, {fn} are two bounded sequences in H introduced to take into account possible in exact computation and the sequences {an}, {/3n}, {Tn}, {6n} in [0, 1] satisfying the following conditions: (1) an+’Tn<_l,n+6n<_l foralln=O, 1,2,..., (2) an O, n -’+ 0 as n c, (3) (C) Mann Type Perturbed Iterative Algorithm (MTPIA) Let f, p, g, m H H and N: H H H be mappings. Given u0 H, the iterative sequence {un} are defined by un+ n)Un + n[Un (g- m)(un) + j"(.,u,)((g_ m)(un) aN(f(Un),p(un)))] (1 (3.4) NONLINEAR IMPLICIT QUASIVARIATIONAL INCLUSIONS - 387 for n 0, 1, 2,..., where M n H x H 2 n is a set-valued mapping such that, for each y E H, M"(., y):H-- 2 /is a maximal monotone mapping for n=0, 1,2,..., a >0 is a constant, the sequence {a} in [0, 1] satisfying the following conditions: (1) a,0 as nec, (2) En=00n (D) Ishikawa Type Perturbed Iterative Algorithm (ITPIA) Let f,p, g, m H H and N: H x H-- H be mappings. Given u0 E H, the iterative sequence {u.} are defined by Un+, On)Un + n[Vn (1 (g- m)(Vn) + jM"(.,,,n)((g_ m)(Vn) aU(f(v,,),p(vn)))], Vn (1 -/n)Un +/n[Un (g- m)(un) + jM"(.,u,)((g_ m)(Un) aN(f(Un),p(un)))] for n 0, 1,2,..., where M H x H-- 2 is a set-valued mapping such that, for each y H, M( y) H 2 t-/is a maximal monotone mapping for n=0, 1,2,..., a >0 is a constant, the sequences {an}, {/3n}, {7}, {} in [0, 1] satisfying the following conditions: ., (1) a- 0 as n (2) oc, Remark 3.1 (1) If /3=n=0 for all n=0,1,2,..., then ITPIAE reduces to MTPIAE. (2) If 3’ 6n 0 for all n 0, 1,2,..., then ITPIAE reduces to ITPIA. (3) If 7, 0 for all n 0, 1,2,..., then MTPIAE reduces to MTPIA. (4) Our ITPIAE includes several known algorithms of[1,6,10,15,16,18] as special cases. 4 EXISTENCE AND CONVERGENCE THEOREMS In this section, we show the existence of a solution of the problem (2.1) and the convergence of iterative sequence generated by ITPIAE. S.H. SHIM et al. 388 DEFINITION 4.1 Let N" H x H-- H and g" H H. (1) g is said to be strongly monotone/f there exists some 6 > 0 such that (g(ul) g(u2), ul for all u E H, u2) _> llul u=ll 1,2; (2) g & said to be Lipschitz continuous if there exkcts some r > 0 such that IIg(u) g(u.)[[ u2 for all ui E H, 1,2; (3) g is said to be strongly monotone with respect to the first argument of N if there exists some # > 0 such that u2) (N(g(u,), .)- N(g(u2), "), Ul for all ui H, [[Ul u2ll 2 1,2; (4) g is said to be Lipschitz continuous with respect to the first argument of N if there exists some > 0 such that N(g(u2), ")11 IIN(g(u), ") llu u211 for all uiH, i= 1,2. In a similar way, we can define strong monotonicity and Lipschitz continuity of g with respect to the second argument of N. DEFINITION 4.2 Let {S n} and S be maximal monotone mappings for n= 1,2,... The sequence {S n} is said to be graph-convergence to S (write S" S) if, for every (x,y) Graph(S), there exists a sequence (xn, y) Graph(S ") such that xn x and y, y in H. LEMMA 4.1 [2] Let n O, 1, 2,... Then S n x H and A > O. - S be maximal monotone mappings for {S} Sand and every only J{" (x) J(x) if if for LEMMA 4.2 [19] Let {an}, {bn} and {cn) be three nonnegative real sequences such that, for all n O, 1,2,..., an+ <_ (1 with O < t < limn an 0. y’n=otn c tn )an -+- bn + Cn o Cn < cxz. Then bn o(tn) and -]n=0 NONLINEAR IMPLICIT QUASIVARIATIONAL INCLUSIONS 389 THEOREM 4.1 Let N: H x H--+ H be a mapping, g, m H-- H be Lipschitz continuous with constants cr and #, respectively, f, p H-- H be Lipschitz continuous with constants rl and e with respect to the first and second arguments of N, respectively, f be strongly monotone with constant/3 with respect to the first argument of N and g-m be strongly monotone with constant Assume that . (m(v) m(u),g(u) g(v)) < llu- vii 2 (4.1) . for all u, v E H andfor some constant ,k such that o < < or#, where Ao inf{s: (m(v) m(u),g(u) g(v)) < s[lu vii 2 for all u, v e H}. Suppose that there exists a constant > 0 such that, for each x, y, z H, IIJM(’’x) (2) jM(.,y)(Z)]l ll x YII" (4.2) If the following conditions hold." 2 + e(k 1) < V/(/3 + (k- 1)e) (r/: e2)k(2 k) 72 e2 (4.3) (4.4) tee< l-k, k=.+2V/1-26+cr2+#2+2A, k<l, (4.5) then the problem (2.1) has a unique solution u* H. Moreover, suppose that M n H H 2 is a set-valued mapping such that, for each y H, M’( y) H---. 2 is a maximal monotone mapping for n O, 1, 2,..., M n (., y) M(., y) and, for each x, y, z H, ., IlJMn(" x) (z)- jMn(.,y) (z)ll <_C[[x-yll. Then {u,} strongly convergences to it u*, where {Un} is ITPIAE. (4.6) defined by S.H. SHIM et al. 390 First we prove that there exists u* E H which is a unique solution of the problem (2.1). By Lemma 3.1, it is enough to show that the mapping F: H H defined by (3.1) has a unique fixed point u* E H. In fact, for any u, v H, we have Proof F(u) u (g m)(u) + j(.,u)((g m)(u) aN(f(u),p(u))) F(v) v (g m)(v) + j(.,v)((g_ m)(v) aN(f(v),p(v))). and From the definition of j(.,u) and (4.2), we have liE(u) F(v) Ilu (g m)(u) + j(.,u)((g m)(u) aN(f(u),p(u))) [v (g- m)(v) + j(.,v)((g m)(v) aN(f(v),p(v)))][[ _< Ilu- v- ((g- m)(u) (g- m)(v))ll / IIJl,ul((g- m)(u) aN(f(u),p(u))) j.,ul((g_ m)(v) N(f(v),p(v)))]ll / IlJ’,ul((g- m)(v) aN(f(v),p(v))) J"((g- m)(v) cN(f(v),p(v)))]ll _< 211u- v- ((g- m)(u) (g- m)(v))]l + u v a(N(f(u),p(u)) N(f(v),p(u)))[[ / llN(f(v),p(u)) N(f(v),p(v))ll / llu vii. (4.7) By (4.1), the Lipschitz continuity off, g, m and strong monotonicity of g- m and f, we obtain Ilu- v- ((g- m)(u) (g- m)(v))ll 2 Ilu- vii 2 2(u v, (g- m)(u) (g- m)(v)) lira(u) m(v)ll 2 / Ilg(u) -g(v)ll = + 2(m(v) m(u),g(u) g(v)) < (1 2 + cr2 + #9. + 2A)IIu vii = / (4.8) NONLINEAR IMPLICIT QUASIVARIATIONAL INCLUSIONS 391 and Ilu a(N(f(u),p(u)) N(f(v),p(u)))ll 2 < (1 2a/3 + a2r/2) Ilu vii 2, v- (4.9) Further, since p is Lipschitz continuous with respect to the second argument of N, we get IIN(f(v),p(u)) N(f(v),p(v))ll <_ ellu- vii. (4.10) From (4.7)-(4.10), it follows that IlF(u)- F(v)]l 5 hllu- (4.11) where h 2 V/1 26 + er2 + #2 + 2, + { + v/1 2c/3 + 022 -1-- Ct. From (4.3)-(4.5), we know that 0 < h < and so F has a unique fixed point u* E H. By Lemma 3.1 and (4.11), we know that u* is a unique solution of the problem (2.1). Next we prove that the iterative sequence {un} defined by ITPIAE strongly converges to u*. Since u* is a solution of the problem (2.1), we have F(u*) u* (g m)(u*) + jM(.,u*)((g_ m)(u*) aN(f(u*),p(u*))). (4.12) It follows from (3.3), (4.12) and Lemma 3.1 that Ilu+, u*ll ]1(1 ogn ")/n)Un -I- Ogn[ltn (g- m)(ln) + jaMn("vn)((g- m)(vn) oU(f(Vn),p(vn)))] + %en (1 on ")’n)U* Ctn[U* (g- m)(u*) + jM"(.,u*)((g m)(u*) oU(f (u*),p(u*)))] + S.H. SHIM 392 < (1 On (u* et al. (g m)(Vn) %)llu. u*ll / anllVn (g m)(u*))[] + %lien u*[I / CnllJ("((g m)(v) jy(.,u*)((g_ m)(u*) N(f(u*),p(u*)))[[ <.(1 an 7n)[lUn u*ll / OnllVn U* ((g- m)(Vn) ((g-- m)(v) (g- m)(u*))ll /’rnlle u*ll + nlI/ oN(f(Vn),p(Vn))) JM"("v)((g m)(u*) cN(f(u*),p(u*)))ll + nllJ"("v)((g- m)(u*) aN(f(u*),p(u*))) .Z_"u*((g m)(u*) N(f(u*),p(u*)))ll / CnllJ"u*l((g- m)(u*) aN(f(u*),p(u*))) jl.,u*l((g m)(u*) N(f(u*),p(u*)))ll _< (1 %)llu u*ll / 2llv u* ((g m)(v) (g m)(u*))ll / tnllVn u*ll / %lle u*ll + cnllVn u* a(N(f(vn),p(Vn)) N(f(u*),p(v)))l oN(f(Vn),p(Vn))) / cllN(f(u*),p(Vn)) N(f(u*),p(u*))II + tnllJ("u*)((g- m)(u*) aN(f(u*),p(u*))) j.,u*l((g_ m)(u*) cN(f(u*),p(u*)))ll. (4.13) By (4.1), the Lipschitz continuity off, g, m and strong monotonicity of g- rn and f, we obtain IIv u* < (1 (g m)(u*))ll 26 + 02 + #2 + 2,)II Vn u* = ((g- m)(Vn) (4.14) and [IVn U* ce(N(f(Vn),p(vn)) N(f(u*),p(Vn)))ll 2 < (1 2c/3 + o2T]2)[lvn u*ll 2. (4.15) NONLINEAR IMPLICIT QUASIVARIATIONAL INCLUSIONS 393 Further since p is Lipschitz continuous with respect to the second argument of N, we get ]lN(f(u*),p(v)) N(f(u*),p(u*))[] <_ e[[Vn u*[[. (4.16) From (4.13)-(4.16), it follows that u*ll (1 Ilu.+, / on u*ll + hcnl]Vn u*ll )llu. o,,b, / .),nile. (4.17) u*ll, where b. IlJM"("*/((g- m)(u*) ozN(f(u*),p(u*))) j(.,u*)((g_ m)(u*) aU(f(u*).p(u*)))l I. Similarly, we have u*ll + hllu u*ll //nbn / n IIf U* I1" ( -/ 6n)llUn [Iv. u*ll (4.18) It follows from (4.17) and (4.18) that [lUn+l--U*II Let M1 (1--OZn--’n / hc.(1 -n-6n + hon(nbn / 6nllfn u*ll) / .b. / 7.lie. u*ll: n > O} sup{IlL and M2 sup{lien u*ll: n > 0}. Since 0 < h < 1, we have I[Un+l u*ll (1 ce,(1 h))llun u*ll + an(h6nM1 + (hfln + 1)bn)/ ynM2. Using Lemma 4.1, we know that bn (4.19) and Lemma 4.2 that un --* u* as n (4.19) . 0 as n cx. If follows from This completes the proof. Remark 4.1 (1) If/3n 6n 0 for all n 0, 1,2,..., then Theorem 4.1 gives the conditions under which the sequence {u} defined by MTPIAE strongly converges to u*. S.H. SHIM et al. 394 (2) If’),n 6n 0 for all n 0, 1, 2,..., then Theorem 4.1 gives the conditions under which the sequence {un} defined by ITPIA strongly , converges to u*. (3) If’),, =/3= =0 for all n=0, 1,2,..., then Theorem 4.1 gives the conditions under which the sequence {u,} defined by MTPIA strongly converges to u*. Acknowledgements The third author was supported in part by ’98 APEC Post-Doctor Fellowship (KOSEF) while he visited Gyeongsang National University, and the second and fourth authors wish to acknowledge the financial support of the Korea Research Foundation made in the program year of 1998, Project No. 1998-015-D00020. References [1] S. Adly, Perturbed algorithm and sensitivity analysis for a general class of variational inclusions. J. Math. Anal. Appl. 201 (1996), 609-630. [2] H. 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