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Let *T* be a tree. The *reducible stem* of *T* is the smallest subtree that contains all branch vertices of *T*. In this paper, we first use a new technique of Gould and Shull [5] to state a new short proof for a result of Kano et al. [10] on the spanning tree with a bounded number of leaves in a claw-free graph. After that, we use a similar idea to prove a sharp sufficient condition for a claw-free graph having a spanning tree whose reducible stem has few leaves.

Let *n* ∈ ℕ. An element (*x*
_{1}, … , *x _{n}
*) ∈

*E*is called a

^{n}*norming point*of

*n*-linear forms on

*E*. For

Norm(*T*) is called the *norming set* of *T*.

Let

In this paper, we classify Norm(*T*) for every

This article indicates another set-theoretic formula, solely in terms of union and intersection, for the set of the limits of any given sequence (net, in general) in an arbitrary *T*
_{1} space; this representation in particular gives a new characterization of a *T*
_{1} space.

We give all solutions of completely multiplicative functions ƒ , g, for which the equation *Ag*(*n* + 1) = *B*ƒ (*n*) + *C* holds for every *n* ∈ ℕ. We also study the equation *G*(*p* + 1) = *F*(*p* − 1) + *D* and we prove some results concerning it.

We consider a graph whose vertices are legally colored using *k* colors and ask if the graph contains a *k*-clique. As it turns out this very special type of *k*-clique problem is in an intimate connection with constructing schedules. The practicality this clique search based construction of schedules is checked by carrying out numerical experiments.

Assume that *A _{j}
*,

*j*∈ {1, … ,

*m*} are positive definite matrices of order

*n*. In this paper we prove among others that, if 0 <

*l I*≤

_{n}*A*,

_{j}*j*∈ {1, … ,

*m*} in the operator order, for some positive constant

*l*, and

*I*is the unity matrix of order

_{n}*n*, then

where *Pk* ≥ 0 for *k* ϵ {1, …, *m*} and

The evolute of a conic in the pseudo-Euclidean plane is the locus of centers of all its osculating circles. It’s a curve of order six and class four in general case. In this paper we discuss and compute the order and class of evolutes of different types of conics. We will highlight those cases that have no analogy in the Euclidean plane.

Fast [12] is credited with pioneering the field of statistical convergence. This topic has been researched in many spaces such as topological spaces, cone metric spaces, and so on (see, for example [19, 21]). A cone metric space was proposed by Huang and Zhang [17]. The primary distinction between a cone metric and a metric is that a cone metric is valued in an ordered Banach space. Li et al. [21] investigated the definitions of statistical convergence and statistical boundedness of a sequence in a cone metric space. Recently, Sakaoğlu and Yurdakadim [29] have introduced the concepts of quasi-statistical convergence. The notion of quasi I-statistical convergence for triple and multiple index sequences in cone metric spaces on topological vector spaces is introduced in this study, and we also examine certain theorems connected to quasi I-statistically convergent multiple sequences. Finally, we will provide some findings based on these theorems.

For a graph *G*, we define the lower bipartite number LB(*G*) as the minimum order of a maximal induced bipartite subgraph of *G*. We study the parameter, and the related parameter bipartite domination, providing bounds both in general graphs and in some graph families. For example, we show that there are arbitrarily large 4-connected planar graphs *G* with LB(*G*) = 4 but a 5-connected planar graph has linear LB(*G*). We also show that if *G* is a maximal outerplanar graph of order *n*, then LB(*G*) lies between (*n* + 2)/3 and 2 *n*/3, and these bounds are sharp.

The motions of a bar structure consisting of two congruent tetrahedra are investigated, whose edges in their basic position are the face diagonals of a rectangular parallelepiped. The constraint of the motion is the following: the originally intersecting edges have to remain coplanar. All finite motions of our bar structure are determined. This generalizes our earlier work, where we did the same for the case when the rectangular parallelepiped was a cube. At the end of the paper we point out three further possibilities to generalize the question about the cube, and give for them examples of finite motions.