We present an elementary proof of the well known theorem that the limit of a levelwise weak equivalence of towers of fibrations of topological spaces is a weak equivalence, without mentioning lim.

This paper uses the National Family Health Survey (NFHS) data collected in 1992-93 to estimate the determinants of child (aged 6 to 14) enrollment and educational attainment of a recent cohort (aged 15 to 19) in India. The analysis produces five major results. First, using an index of assets as a proxy for household wealth shows enormous gaps between the enrollment and attainment of children fr...

This paper introduces a class of graphs deened as the models of a peculiar kind of linear bounded machines that read their input performing all computations on work tapes. It is proven that this class is closed, up to observational equivalence, under synchronized product. The rst{order theory of these graphs is investegated and shown to be undecidable. The latter result extends to any logic in ...

the aim of this paper is to study co-prolongations of central extensions. we construct the obstruction theory forco-prolongations and classify the equivalence classes of these by kernels of homomorphisms between 2-dimensional cohomology groups of groups.

Tutte has described in the book “Connectivity in graphs” a canonical decomposition of any graph into 3-connected components. In this article we translate (using the language of symbolic combinatorics) Tutte’s decomposition into a general grammar expressing any family G of graphs (with some stability conditions) in terms of the subfamily G3 of graphs in G that are 3-connected (until now, such a ...