We show that hitting set and set cover problems with half-strips oriented in two opposite directions are NPcomplete.

This paper investigates whether investors are compensated for the tax burden of equity securities. Effective tax rates on equity securities vary over time due to frequent tax reforms and cross-sectionally due to persistent differences in propensities to pay dividends. The paper finds an economically and statistically significant relationship between risk-adjusted stock returns and effective per...

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Model based diagnosis finds a growing range of practical applications, and significant performance-wise improvements have been achieved in recent years. Some of these improvements result from formulating the problem with maximum satisfiability (MaxSAT). Whereas recent work focuses on analyzing failing observations separately, it is also the case that in practical settings there may exist many f...

In the course of history, a large number of politicians have been assassinated. To investigate this phenomenon, rational choice hypotheses are developed and tested using a large data set covering close to 100 countries over a period of 20 years. Several strategies, in addition to security measures, are shown to significantly reduce the probability of politicians being attacked or killed: extend...

Using a longitudinal data set covering the period 1987–2000, the authors explore the impact of female employers and gender segregation on wages in Portugal. In the context of Becker’s (1957) taste for discrimination theory, they investigate whether the gender of a firm manager affects gender wage differences. They find that females benefit from higher wages in female-led firms than in male-led ...

Given a set V of elements, S a family of subsets of V , and G a connected graph on vertex set S,a connected set cover (CSC) is a subfamily R of S such that every element in V is covered by at least one set of R, and the subgraph G[R] of G induced by R is connected. If furthermore G[R] is k-connected and every element in V is covered by at least m sets inR, thenR is a (k,m)-CSC. In this paper, w...