Consider the graph Mn, where n = 2r ≥ 6, consisting of a polygon of length n and all n/2 chords joining opposite pairs of vertices. This graph has 2r vertices which we denote by 1, 2, 3,..., 2r, and the 3r (undirected) edges

We call Mn the n-ladder, defined thus far only for n even. The three smallest n-ladders with n even are shown in Figure 1.

We use the terminology of [1]. Let D be a strongly connected digraph on n points and containing m lines, and let A = A(D) be the corresponding adjacency matrix, so that A is an n x n 0-1 matrix containing m unit elements. We recall that A and D are said to be p-cyclic if p is the greatest common divisor of the lengths of all directed cycles of D. Clearly, the larger the value of p, the smaller the value of m must be; in this note we make the latter and related statements precise.

To each tournament Tn with n nodes n there corresponds the automorphism group G(Tn) consisting n of all dominance preserving permutations of the set of nodes. In a recent paper [3], Myron Goldberg and J. W. Moon consider the maximum order g(n) which the group of a tournament with n nodes may have. Among other results they prove that

1

2

Throughout this paper (X, d) will be a metric space with metric d, and h a homeomorphism of X onto itself. For any real number r > 0, and p ∊ X, U(p, r) will denote the open r - sphere about p. Any point p ∊ X is called regular [3] if for any given ∊ > 0 there exists a δ > 0 such that d(p, y) <δ implies d(hn(p), hn(y)) < ∊ for all integers n, where hn denotes the iterates of h for n > 0, of h-1 for n < 0, and h0 is the identity. Any point of X which is not a regular point i s called an irregular point. Let I(h) denote the set of all the irregular points of X and R(h) = X-I(h). Lim inf and Lim sup are defined as in [4].

Let Ⓗ be an abstract space and for every positive integer n let Fn, θ(x, y), θ ∈ Ⓗ, be a family of distribution n, 0 function s of random variables (Xn, Yn)θ, θ ∈ Ⓗ. For every θ ∈ Ⓗ, Eθg (Xn, Yn) will denote the expected value of the function g of (Xn, Yn )θ. The following proposition is proved.

Let μ∗ be an outer measure on (X, S) with σ- algebra S and let μ* be the inner measure induced by μ∗. A set M is a measurable cover of a set A ⊆ X if A ⊆ M, M is measurable, and μ∗ (M-A) = 0. We assume that every subset of X has a measurable cover; this holds, for example, if μ∗ is the outer measure induced by a measure which is σ- finite on X [2, theorem C, p. 50].

A vector measure (countable additive set function with values in a Banach space) on a field may be extended to a vector measure on the generated σ- field, under certain hypotheses. For example, the extension is established for the bounded variation case [2, 5, 8], and there are more general conditions under which the extension exists [ 1 ]. The above results have as hypotheses fairly strong boundedness conditions on the n o rm of the measure to be extended. In this paper we prove an extension theorem of the same type with a restriction on the range, supposing further that the measure is merely bounded. In fact a vector measure on a σ- field is bounded (III. 4. 5 of [3]) but it is conceivable that a vector measure on a field could be unbounded.

In 1955, Suranyi and P. Turán [8] considered the problem of existence and uniqueness of interpolatory polynomials of degree ≤ 2n-1 when their values and second derivatives are prescribed on n given nodes. Around this kind of interpolation - aptly termed (0, 2) interpolation - considerable literature has grown up since then. For more complete bibliography on this subject we refer to J. Balazs [3], Later we considered [10] the problem of modified (0, 2) interpolation when 2 the abscissas are the zeros of (1-x2) Tn(x), where Tn(x) is the Tchebycheff polynomial of the first kind (Tn(x) = cos n θ, x = cos θ).

In 1955, J. Suranyi and P. Turán [8] introduced the nomenclature (0, 2)-interpolation for the problem of finding polynomials of degree ≤ 2n-1 whose values and second derivatives are prescribed in certain given nodes. In a series of papers ([2], [3], [8]) Professor Turán and his associates discussed the problems of existence, uniqueness, explicit representation and convergence of such interpolatory 2 polynomials when the nodes are the zeros of (1-x2) P′n- 1(x), Pn- 1(x) being the Legendre polynomial of degree n - 1.

In 1940, I. Niven [2] proved that the gaussian integer z = x + iy is the sum of two squares of gaussian integers if, and only if, y is even and not both of 1/2x and 1/2y are rational odd integers. In this note we calculate the total number g2(z) of representations of z in this form.

1

where a, b, c, d are rational integers, if and only if

2

Let d denote a fixed integer > 1 and let GF(q) denote the finite field of q = pn elements. We consider q fixed ≥ A(d), where A(d) is a (large) constant depending only on d. Let

1

where each aiεGF(q). Let nr(r = 2, 3, …, d) denote the number of solutions in GF(q) of

for which x1, x2, …, xr are all different.

Let p denote a prime number and let κp denote the finite field of p elements. Let f(x) ∊ κp[x] be of fixed degree d ≥ 2. We suppose that p is also fixed, large compared with d, say, p ≥ p0(d). By V(f) we denote the number of distinct values of f(x), x ∊ κp. We call f maximal if V(f) = p and quasi-maximal if V(f) = p + O(1). Clearly a maximal polynomial is quasi-maximal but it is not known under what conditions the converse holds.

Let R be a topological (Hausdorff) ring such that for each a ∊ R, aR and Ra are closed subsets of R. We will prove that if the set of non - trivial right (left) zero divisors of R is a non-empty set and the set of all right (left) zero divisors of R is a compact subset of R, then R is a compact ring. This theorem has an interesting corollary. Namely, if R is a discrete ring with a finite number of non - trivial left or right zero divisors then R is a finite ring (Refer [1]).

Hall and Puckett [2] have shown that an arc - preserving function defined on a locally connected continuum having no local separating points is a homeomorphism if its total image is not an arc or point. This note shows that their results can be extended to non-compact manifolds.

In this note we study dependence in matroids as an exercise in combinational algebra. Because the work seems to have little connection with graph theory we will not use Tutte′s approach (1) which uses dual concepts. To define a matroid we use Edmunds (2).