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51.
ABSTRACT. Total cleared area in a von Thünen land-use model drives an atmosphere externality which depresses agricultural productivity uniformly throughout the region. Exogenous events that encourage clearance and use of a larger cultivated area (output price or population increase) exacerbate the externality. Imposition of a simple, corrective tax on land rents does not reverse these patterns but does mitigate the increase in the externality and leaves cultivators with higher incomes than they would obtain without the tax. We examine an optimal tax on land rents, designed to maximize the social value of land rents in the region, and an output tax.  相似文献   
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The Greek Neolithic, here divided into five phases, is the oldest in Europe. Geographically, it is the closest to the Near East and has thus long been seen as an impoverished derivative of the latter. However, recent research has tended to emphasize the autochthonous nature of Neolithic development in Europe, including Greece. The Greek Neolithic economy, which was based almost entirely on domesticates, and its densely packed, long-lived villages strongly recall the Near East, as do also the early emphasis on fine, decorated, nonculinary pottery and the wealth of figurines. On the other hand, the evolution of stylistic patterns is specifically Greek, although generally related to trends in the Balkans. Originality in the development of the Greek Neolithic is also seen in its latest phase, with apparent decreases, rather than increases, in site density, social differentiation, and, to some extent, long-distance trade. At the same time, however, the dichotomy became much sharper between the rich agricultural plains of northern Greece and the more pastoral(?) regions of the Peloponnese and Cycladic Islands; this presages similar contrasts during the Bronze Age.  相似文献   
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In skeletons excavated from Woodland sites, copper and barium levels are found to have been contaminated by influx from the soil environment. Electron microprobe scans for both elements show build-up along the outer surface of femur cross sections. Elemental levels for Cu and Ba are lower in the femur or fibula than in the more porous rib. The distribution of Cu in the immediately surrounding soil is highly anisotropic. These observations indicate that Cu and Ba should not be used for dietary inferences about ancient populations without independent evidence that diagenesis is not important.  相似文献   
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High-precision neutron activation measurements have been made on mesoamerican obsidian from Ixtepeque and El Chayal which are thought to be the major sources of volcanic glass artifacts in pre-Columbian times. These results are compared with measurements on obsidian artifacts from Lubaantun, Wild Cane Cay, Frenchman's Cay and Moho Cay.  相似文献   
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