International Journal of Scientific & Engineering Research, Volume 5, Issue 2, February-2014 8
ISSN 2229-5518
SANDWICH-TYPE THEOREMS FOR MEROMORPHIC MULTIVALENT FUNCTIONS ASSOCIATED WITH A LINEAR OPERATOR
H. E. Darwish, A. Y. Lashin, and B. H. Rizqan
Abstract— the purpose of this article is to obtain some subordination and superordination preserving properties of meromorphic
p
multivalent functions in the punctured open unit disk associated with the linear operator meromorphic multivalent functions are also considered.
Qα , β , γ
the sandwish- type results for these
2010 Mathematics Subject Classification: Primary 30C45.
Keywords— Meromorphic function, Hadamard product, Subordination, Superordination, Meromorphic multivalent function, Linear operators,
Sandwich result.
—————————— ——————————
open unit disk
U = {z ∈ C :
z < 1}.
a dominant, if
p q
for all p satisfying (1.1). A domnant
ET H (U)
denote the class of analytic functions in the
solutions of the differential subordination, or more simply
For n ∈ N = {1, 2,...}
and
a ∈ C,
let
that satisfies for all dominants q of (1.1) is said
H [a, n] = { f ∈ H :
f ( z) = a + an
z n + a
n+1
z n+1 + ...}.
to be the best dominant.
Let f and F be members of
H . the function f is
Definition 2 [10]. Let ϕ
: C 2 → C
and let h be analytic
said to be subordinate to
F , or F is said to be superordi-
in U . If p and
ϕ ( p( z), zp′( z))
are univalent in U
nate to f , if there exists a function w analytic in U ,
and satisfy the differential superordination:
with w(0) = 0
and
w( z) < 1
( z ∈ U),
such that
h( z) ϕ ( p( z), zp′( z))
( z ∈ U),
(1.2)
f ( z) = F (w( z))
( z ∈ U).
then p is called a solution of the differential superordination.
An analytic function q is called a subordinant of the
In such a case, we write
soltions of the differential superordination, or more simply
f F
( z ∈ U) or
f ( z) F ( z)
( z ∈ U).
a subordinant if
q p
for all p satisfying (1.2). A uni-
If the function F is univalent in U , then we have (cf. [11])
f ( z) F ( z)
( z ∈ U) ⇔
f (0) = F (0)
vlent subordinant that for all subordinants q of
(1.2) is said to be the best subordinant.
and
f (U) ⊂ F (U).
Definition 3 [10]. Denote by Q the class of functions f
Definition 1 [9]. Let φ
: C 2 → C
and let h be univalent
that are analytic and injective on
U \ E( f ),
where
in U . If p is analytic in U and satisfies the differential
subordination:
E( f ) = {ζ ∈ ∂U
: lim f ( z) = ∞},
z →ζ
φ ( p( z), zp′( z)) h( z)
( z ∈ U),
(1.1)
and are such that
then p is called a solution of the differential subordination.
The univalent function q is called a dominant of the
f ′(ζ ) ≠ 0(ζ ∈ ∂U \ E( f )).
For any integer
m > − p,
Let
Σ p , m
denote the class of
————————————————
Department of Mathematics, Faculty of Science,
all meromorphic functions f of the form
∞
• H. E. Darwish, Mansoura University, Mansoura, Egypt
• Y. Lashin, Mansoura University, Mansoura, Egypt
f ( z) = z − p + ∑ a z k
k =m
( p ∈ N = {1, 2,...}),
(1.3)
E-mail: aylashin@mans.edu.eg
• B. H. Rizqan, Mansoura University, Mansoura, Egypt E-mail :
which are analytic and p -valent in the punctured unit disk
bakeralhaaiti@yahoo.com
U ∗ = {z ∈ C :
0 < z
< 1} = U \ {0}.
For convenience, we
write
Σ p ,1− p = Σ p .
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International Journal of Scientific & Engineering Research, Volume 5, Issue 2, February-2014 9
ISSN 2229-5518
For functions
f ∈ Σ p , m
given by (1.3), and
g ∈ Σ p , m
If is not subordinate to , then there exist points
iθ
defined by
∞
z0 = r0 e
∈ U and ζ 0 ∈ ∂U \ E( f ),
g ( z) = z − p + ∑ b z k
=
(m > − p; p ∈ N),
(1.4)
for which
q(U
) ⊂ p(U),
q( z
) = p(ζ )
k m r0 0 0
then the Hadamard product (or convolution) of f and g
is
and
z0 q′( z0
) = mζ 0
p′(ζ 0 )
(m ≥ n).
∞ A function
L( z, t )
defined on
U × [0, ∞),
is the subordi-
( f ∗ g )( z) = z − p + ∑ a b z k
= ( g ∗ f )( z)
nation chain (or Löwner chain) if
L( z,.)
is analytic and uni-
k k
k =m
(1.5)
valent in U for all
t ∈ [0, ∞),
L( z,.)
is continuously
(m > − p; p ∈ N).
Differentiable on
[0, ∞)
for all
z ∈ U
and
For
f ∈ Σ p , m
we now define the integral operator
L( z, s) L( z, t )
( z ∈ U; 0 ≤ s < t ).
p
α , β , γ
: Σ p , m
→ Σ p , m
which was introduced and studied
by El-Ashwah et al. [3] as follows:
q ∈ H[a,1]
and ϕ
: C 2 → C.
Q p f ( z) =
Γ(α + β − γ + 1) 1 ⋅
Also set
α , β , γ
Γ(β )Γ(α − γ + 1) z β + p
ϕ (q( z), zq′( z)) ≡ h( z)
( z ∈ U).
z α −γ
If L( z, t ) = ϕ (q( z), tzq′( z))
is a subordination chain and
− t t
f t dt
p ∈ H[a,1] ∩ Q,
1
0 z
β + p −1 ( )
then.
= 1 + Γ(α + β − γ + 1) ⋅
z p Γ(β )
∞ Γ(β + p + k )
∑
a z k
(1.6)
implies that
h( z) ϕ ( p( z), zp′( z))
( z ∈ U).
k =m
Γ(α + β + p + k − γ + 1)
Furthermore, if
ϕ (q( z), zp′( z)) = h( z)
has a univalent
and
p
(β > 0; α > γ − 1; γ
> 0;
p ∈ N;
z ∈ U∗ ),
∗
solution
q ∈ Q,
then q is the best subordinate.
2
Qα −1, β , γ f ( z) =
f ( z)
(β > 0; γ
> 0;
p ∈ N;
z ∈ U ).
From (1.6), it is easy to verify that
p p
satisfies the following condition:
Re{H (is, t )} ≤ 0
z(Qα +1, β , γ f ( z))′ = (α + β − γ + 1)Qα , β , γ f ( z) −
(α + β + p − γ + 1)Q p f ( z).
(1.7)
for all real s and
t ≤ −n(1 + s 2 ) / 2
(n ∈ N).
If the function
p( z) = 1 + pn
z n + ....
is analytic in U and
Remark:
p p
p Re{H ( p( z), zp′( z))} > 0
( z ∈ U),
(i) For
γ = 1, Qα , β ,1 = Qα , β ,
where the operator
Qα , β
then
was introduced and studied by Aqlan et al. [2] (see also [1]);
Re{ p( z)} > 0
( z ∈ U).
1 p
(ii) For
p = γ
= 1, Qα , β ,1 = Qα , β ,
where the operator
Qα , β ,
was introduced and studied by Lashin [6].
β , γ ∈ C
with
β ≠ 0
and
h ∈ H(U)
with
h(0) = c.
If
Re{βh( z) + γ } > 0
( z ∈ U),
The following lemmas will be required in our present
then, the solution of the differential equation
investigation.
p ∈ Q
with
p(0) = a
and let
q( z) +
zq′( z)
βq( z) + γ
= h( z)
( z ∈ U;
q(0) = c),
q( z) = a + an
z n + .....
is analytic in U satisfies the inequality
be analytic in U with
Re{βq( z) + γ } > 0
( z ∈ U).
q( z) ≠ a
and
n ≥ 1.
L( z, t ) = a1 (t ) z + ...
with
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ISSN 2229-5518
a1 (t ) ≠ 0
and
lima1 (t )
= ∞
t →∞
is a subordination chain if
then,
Re{q( z)} > 0
( z ∈ U).
and only if
z∂L( z, t )
Taking the logarithmic differentiation on both sides of the se- cond equation in (3.5) and using the equation (1.7) we obtain
Re > 0
( z ∈ U; 0 ≤ t < ∞),
p(α + β − γ )φ ( z) = p(α + β − γ )G( z) + ( p − η ) zG′( z).
=∂L( z, t )
(3.7)
and
∂t
Now, by differentiating both sides of (3.7), We obtain the rela- tionship:
L( z; t ) ≤ K 0 a1 (t ) ,
z < r0 < 1, t ≥ 0,
1 + zφ ′ ( z) = 1 + zG′ ( z) +
zq′( z)
φ ′( z)
G′( z)
q( z) + p(α + β − γ ) /( p − η )
For some positive constants
a subordination chain.
K 0 and
r0 , then
L( z, t ) is
= q( z) +
zq′( z)
q( z) + p(α + β − γ ) /( p − η )
≡ h( z).
(3.8)
We also note from (3.1) that
We begin with proving the following subordination theorem
p
Reh( z)
+ p(α + β − γ
p −η
)
> 0
( z ∈ U),
involving the operator
Qα , β , γ f ( z)
defined by (1.6).
and so by Lemma 4, we conclude that the differential equation
(3.8) has a solution
q ∈ H(U)
with
f , g ∈ Σ p , m , α > γ ,
β > 0, γ
> 0,
p ∈ N,
0 ≤ η < p
q(0) = h(0) = 1.
and
z ∈ U.
Suppose that
zφ ′
Re1 +
( z)
> −δ ,
(3.1)
Let us put
H (u, v) = u +
v + δ
u + p(α + β − γ ) /( p − η )
(3.9)
setting
where
φ ′( z)
where δ is given by (3.2).
From (3.1), (3.8) and (3.9), we obtain
Now, we proceed to show that
( p − η ) 2 + p 2 (α + β − γ ) 2
Re{
( , )} 0 ;
1 (1
2 ) .
δ = −
4 p( p − η )(α + β − γ )
H is t ≤
s ∈ R
t ≤ −
2
+ s
(3.10)
( p − η ) 2 − p 2 (α + β − γ ) 2
(0 < δ ≤ 1/ 2).
(3.2)
Indeed, From (3.9), we have
t
Re{H (is, t )} = Reis +
+ δ
4 p( p − η )(α + β − γ )
is + p(α + β − γ ) /( p −η )
Then, the following subordination relation
= tp(α + β − γ ) / p − η + δ
p(α + β − γ ) /( p − η ) + is 2
implies that
(3.3)
≤ − Eδ (s) ,
2 p(α + β − γ ) /( p − η ) + is 2
(3.11)
z p Q p f ( z) z
p p
α , β , γ
( z ∈ U).
(3.4)
where
p p p α + β − γ
p α β γ
Moreover, the function
z Qα , β , γ g ( z)
is the best dominant.
E (s) := (
) − 2δ s 2 − ( +
− ) ⋅
Proof. Let us define the functions F and G,
δ
respectively,
p − η
p − η
by
F ( z) := z
Qα , β , γ f ( z)
and
G( z) := z
Qα , β , γ g ( z). (3.5)
2δ
p(α + β − γ )
.
p − η
(3.12)
We first show. If the function is defined by
q( z) := 1 + zG ′ ( z)
( z ∈ U),
(3.6)
For δ given by (3.2), we can prove easily that the expression
G ′( z)
Eδ (s)
given by (3.12) is greater than or equal to zero. Hence,
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from (3.9), we see that (3.10) holds true. Thus using Lemma 3, we conclude that.
L(ζ
0 , t ) = G(ζ
) + ( p − η )(1 + t ) ζ
0 p(α + β − γ )
0 G′(ζ 0 )
Re{q( z)} > 0
( z ∈ U).
= + p − η
Moreover, we see that the condition:
G′(0) ≠ 0
F ( z0 )
p(α + β − γ )
z0 F ′( z0 )
is satisfied. Hence, the function defined by (3.5) is convex
( p − η ) p p
( ) η p p
( ) ( ),
in U.
= z0 Qα , β , γ f z0
p
+ z0 Qα , β , γ f p
z0 ∈ φ U
Next, we prove that the subordination condition (3.3) implies
by virtue of the subordination condition (3.3). This contra-
that
dicts the above observation
L(ζ 0 , t ) ∉ φ (U). Therefore, the
F ( z) G( z)
( z ∈ U)
(3.13)
subordination condition (3.3) must imply the subordination
for the functions F and G defined by (3.5). Without loss
given by (3.13). Considering
F ( z) = G( z), we see that the
of generality, we can assume that G is analytic and univa-
lent on U and
function G is the best dominant. This evidently completes the proof of Theorem 1.
G′(ζ ) ≠ 0
(ζ ∈ ∂U).
We next provide a dual problem of Theorem 1, in the
For this purpose, we consider the function
L( z, t )
given by
sense that the subordinations are replaced by superordina-
tions.
L( z, t ) := G( z) + ( p − η )(1 + t ) zG′( z)
p(α + β − γ )
(0 ≤ t < ∞; 0 ≤ η < p;
z ∈ U).
f , g ∈ Σ p , m , α > γ ,
β > 0, γ
> 0,
p ∈ N,
0 ≤ η < p
We note that
∂L( z, t )
= G′(0) ⋅
and
z ∈ U.
Suppose that
Re1 +
zφ ′
( z)
> −δ ,
∂z z =0
φ ′( z)
p α + β − γ
+ p − η
+ t
setting
( ) (
)(1
) ≠ 0.
p − η η
(α + β − γ )
φ ( z) :=
z Qα
p
, β , γ g ( z) +
z Qα , β , γ g ( z),
p
This shows that the function
L( z, t ) = α1 (t ) z + ...
−
where δ is given by (3.2), and
p − η η
satisfies the condition
α1 (t ) ≠ 0
(0 ≤ t < ∞).
p p
p α −1
, β , γ f ( z) +
z p Q p f ( z),
p
p p
α β γ
∈ H ∩
Then,
Furthermore, we have
is univalent in U and
z Q , ,
f ( z)
[1,1] Q.
Re z∂L(
z, t) /
∂z
=
the following superordination relation
∂L( z, t) / ∂t
φ ( z)
p − η z p Q p
f ( z) + η z p Q p
f ( z) ( z ∈ U),
p α + β − γ
zG′ z
p α −1 , β , γ
p α , β , γ
( Re
) + (1 + t )1 +
( ) > 0.
(3.14)
p − η
G′( z)
implies that
p p p p
Therefore, by virtue of Lemma 5,
L( z, t )
is a subordination
z Qα , β , γ g ( z) z
p
Qα , β , γ f ( z)
p
( z ∈ U).
chain. We observe from the definition of subordination chain
that
Moreover, the function
z Qα , β , γ g ( z)
is the best subordi-
L(ζ , t ) ∉ L(U, 0) = φ (U)
(ζ ∈ ∂U; 0 ≤ t < ∞).
nant.
Proof. The first part of the proof is similar to that of Theorem 1
Now, suppose that F is not subordinate to G,
then by
and so we will use the same notation as in the proof of
Lemma 1, there exists points
that
z0 ∈ U
and
ζ 0 ∈ ∂U,
such
Therem1.
Now, let us define the functions F and G by (3.5). We
q is defined by (3.6), using
F ( z0 ) = G(ζ 0 )
(0 ≤ t < ∞).
and
z0 F ( z0 ) = (1 + t )ζ 0 G′(ζ 0 )
first note that, if the function
(3.7), then we obtain
Hence, we have
φ ( z) = G( z) +
p − η zG′
p(α + β − γ )
:= ϕ (G( z), zG′( z)).
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(3.15) Then using the same method as in the proof of Theorem 1.
p p
α , β , γ 2
are the best subordinate and the best
We can prove that
Re{q( z)} > 0
( z ∈ U),
dominant, respectively.
The assumption of Theorem 3, that the functions
that is, G defined by (3.5) is convex (univalent) in U . Next, we prove that the subordination condition (3.14) implies that
need to be univalent in U , may be replaced by another
G( z) F ( z)
(3.16)
( z ∈ U)
condition in the following result.
for the functions F and G defined by (3.5). Now, consider
Corollary 1. Let
the function
L( z, t )
defined by
f , g k ∈ Σ p , m
(k = 1, 2), α > γ ,
β > 0, γ
> 0,
p ∈ N,
L( z, t ) := G( z) +
( p − η )t
zG′( z)(0 ≤ t < ∞;
z ∈ U).
0 ≤ η < p
p(α + β − γ )
and
z ∈ U.
Suppose that condition (3.17) is satisfied and
As G is convex and
p(α + β − γ ) /( p − η ) > 0,
we can
Re1 +
zψ ′
( z)
> −δ ,
(3.18)
prove easily that
L( z, t )
is a subordination chain as in the
ψ ′( z)
proof of Theorem 1. Therefore, according to Lemma 2, we conclude that the superordination condition (3.14) must
setting
ψ ( z) :=
p − η z p Q p
f ( z) + η z p Q p
f ( z),
imply the superordination given by (3.16). Furthermore, as
the differential equation (3.15) has the univalent solution
p α −1 , β , γ
p α , β , γ
G , it is the best subordinate of the given differential su-
where δ is given by (3.2). Then, the following relation
perordination. Therefore, we complete the proof of Theo- rem 2. If we combine Theorems 1 and 2, then we obtain the
φ1 ( z)
p − η
p
p p
α −1
, β , γ f ( z) +
η z p
p
p
α , β , γ
following sandwich -type theorem.
φ2 ( z)
implies that
( z ∈ U),
f , g k ∈ Σ p , m
(k = 1, 2), α > γ ,
β > 0, γ
> 0,
p ∈ N,
0 ≤ η < p
Moreover, the function
z Qα , β , γ g1 ( z)
and
and
z ∈ U.
Suppose that
′′
p p
α , β , γ
g 2 ( z)
are the best subordinate and the best
zφ ( z)
Re1 + k > −δ ,
(3.17)
dominant, respectively.
φ ′ ( z)
Proof. To prove Corollary 1, we have to show that condi-
ψ and
setting
tion (3.18) implies univalent of
p p
( z)
F ( z) := z
Qα , β , γ g1 ( z).
As 0 < δ ≤ 1 / 2
from Theorem 1, condition (3.18) means
where δ is given by (3.2), and
that ψ is a close- to-convex function in U (see [4]) and
p − η
p
p p
α −1
, β , γ f ( z) +
η z p
p
Q p f ( z),
hence ψ is univalent in U . Furthermore, using the same techniques as in the proof of Theorem 1, we can prove the
is univalent in U and the following relation
z Qα , β , γ f ( z) ∈ H[1,1] ∩ Q.
Then,
convexity (univalent) of F and so the details may be omit- ted here. Therefore, by applying Theorem 3, we obtain
Corollary1.
φ1 ( z)
p − η
p
p p
α −1
, β , γ f ( z) +
η z p
p
p
α , β , γ
φ2 ( z)
( z ∈ U)
f , g k ∈ Σ p , m
(k = 1, 2), α > ( p − η ) / p,
0 ≤ η < p
Implies that
and
z ∈ U .
Suppose that
zφ ′′ ( z)
p p Re1 + ′
> −δ ,
(3.19)
Moreover, the function
z Qα , β , γ g1 ( z)
and
φk ( z)
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ISSN 2229-5518
setting
z p Q p F ( z) ∈ H[1,1] ∩ Q.
Then, the following relation
φk ( z) :=
p − η
p +1 p
α
, β , γ
g k ( z) +
η z p +1
p
α , β , γ
g k ( z),
φ ( z) z
p Q p
f ( z) φ
( z)
( z ∈ U)
p −1 p
where
1
Implies that
p p
α , β , γ 2
p p
( p − η ) 2 + ( p(α + β − γ − 1) + η ) 2
z Qα , β , γ Fµ ( g1 )( z) z
Qα , β , γ Fµ ( f )( z)
δ = −
4( p − η )( p(α + β − γ − 1) + η )
z Q p F ( g )( z)
( z ∈ U).
( p − η ) 2 − ( p(α + β − γ − 1) + η ) 2
Moreover, the functions
z p Q p F ( g )( z)
and
,
4( p − η )( p(α + β − γ − 1) + η )
z p Q p F ( g )( z)
are the best subordinate and the best
and
p − η
p +1 p
α
, β , γ f ( z) +
η z p +1
Q p f ( z),
dominant, respectively.
Proof. Let us define the functions F and Gk
(k = 1, 2) by
p −1
p
p +1 p
F ( z) := z p Q p
Fµ ( f )( z)
Is univalent in U and z
Qα , β , γ f ( z) ∈ H[0,1] ∩ Q.
and
G ( z) := z p Q p
Fµ ( g k
)( z),
Then, the following relation
respectively. Without loss of generality, as in the proof of
φ1 ( z)
p − η
p
z p +1
p
α −1
, β , γ f ( z) +
η z p +1
p
p
α , β , γ
Theorem 1, we can assume that Gk
univalent on U , and
is analytic and
φ2 ( z)
( z ∈ U),
Implies that
G′ (ζ ) ≠ 0
(ζ ∈ ∂U).
z p +1
Q p g ( z) z
p +1
p
α , β , γ
From the definition of the integral operator
Fµ defined by
p +1
p
α , β , γ 2
( z ∈ U).
(3.20), we obtain
z(Q p
F ( f )( z))′ = µQ p
f ( z) −
Moreover, the functions z
p +1
p
α , β , γ 1
and dominant,
α , β , γ µ
p
α −1 , β , γ
respectively.
Next, we consider the integral operator by (ef. [5],[12])
z
µ + p −1
Fµ (µ > 0)
defined
(µ + p)Qα , β , γ Fµ ( f )( z).
Then, from (3.21) and (3.23), we have
µφ ( z) = µG ( z) + zG′ ( z).
Setting
(3.23)
(3.24)
Fµ ( f )( z) := µ + p ∫ t
0
f ( z)dt
( f ∈ Σ p , m ;
µ > 0)
(3.20)
zG′′ ( z)
q ( z) = 1 + k
k G′ ( z)
(k = 1, 2;
z ∈ U),
(3.25)
Now, we obtain the following result involving the integral
operator defined by (3.20).
k
And differentating both sides of (3.24), we obtain
f , g k ∈ Σ p , m
(k = 1, 2).
Suppose also
zφ ′′
1 + k
′
( z) = q
( z) +
zq′ ( z)
k .
q ( z) + µ
that
φk ( z) k
Re1
zφ ′′
+ k
( z)
> −δ
The remaining part of the proof is similar to that of
Theorem 1 and so is omitted the proof involved.
Setting
(3.21)
p p
φ ′ ( z)
[1] M. K. Aouf, A. Shamandy, A. O. Mostafa and F. Z. El-Emam, "On certain subclasses of meromorphically p-valent functions associated with integral op-
where
φk ( z) := z
Qα , β , γ g k ( z); k = 1, 2; z ∈ U,
erators", European J. Pure Appl. Math., 4 (2011), no. 4, 435-447.
[2] E. Aqlan, J. M. Jahangiri and S. R. Kulkarni, "Certain integral operators ap- plied to meromorphic p-valent functions", J. Nat. Geom., 24 (2003), 111-120.
1 + µ 2 − 1 − µ 2
δ =
4µ
p p
(µ > 0),
(3.22)
[3] R. M. El-Ashwah, M. K. Aouf and Ahmed M. Abd-Eltawab, "Applications of differential subordination on certain subclasses of p-valent meromorphic functions", An. Univ. Oradea Fasc. Mat., 20 (2013), no. 1, 125-136.
[4] W. Kaplan, "Close-to-convex schlicht functions", Michigan Math. J., 2 (1952),
and
z Qα , β , γ f ( z)
is univalent in U and
169-185.
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ISSN 2229-5518
[5] V. Kumar and S. L. Shukla, "Certain integrals for classes of p-valent functions", Bull. Austral Math. Soc., 25 (1982), 85-97.
[6] A. Y. Lashin, "On certain subclasses of meromorphic functions associated with certain integral operators", Comput. Math. Appl., 5 (2010), 524-531.
[7] S. S. Miller and P. T. Mocanu, "Differential Subordination and univalent func- tions", Michigan Math. J., 28 (1981), 157 -171.
[8] S. S. Miller and P. T. Mocanu, "Univalent solutions of Briot-Bouquet differen- tial equations", J. Different Eq., 57 (1985), 297-309.
[9] S. S. Miller and P. T. Mocanu, "Differential Subordination. Theory and Appli- cations", Series on Monographs and Textbooks in Pure and Applied Mathe- matics, Vol. 225, Marcel Dekker, New York and Basel, 2000.
[10] S. S. Miller and P. T. Mocanu, "Subordinates of differential superordinations", Complex Var Theory Appl, 48 (2003), 815-826.
[11] C. Pommerenke, "Univalent functions", Vanderhoeck and Ruprech, Göttin- gen, 1975.
[12] H. M. Srivastava and S. Owa, "Current Topics in Analytic Function Theory", World Scientific Publishing Company, Singapore, New Jersey, London, Hong
Kong, 1992.
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