沙中精魂

从空中俯瞰，刻画在沙漠上的线条仿佛长时间暴露在阳光下的画作，轮廓已模糊难辨。飞行员在秘鲁南部纳斯卡镇以北的荒漠高原上空急转盘旋，我只能依稀辨出地面上一系列描绘精美的图形。     

瑞典早期关于中国边疆研究概况

随着13世纪蒙古军队越来越接近欧洲,欧洲人便开始注意中国的边疆地区了.在罗马教皇使节普兰·德·迦儿宾及其后继者带着关于这一地区及其民族的第一手资料返回之前,还没有任何人真正了解这一地区。在马可·波罗长期熟悉了解了这一辽阔的疆域返回欧洲以后,公众对这一地区的兴趣进一步高涨起来。但14世纪以后,欧洲对该地区的了解和兴趣又停滞不前了。只是在西伯利亚殖民化并紧接着恢复了与这些地区的接触后.欧洲才又重新燃起了对它     

A dynamic model of regional population growth and decline

"This paper presents a two-sector dynamic model of regional population change. The model contains a migration equation, an earnings equation, and an amenity equation for each region. In the context of this model, migration is seen as a disequilibrium process through which the regional populations move towards equilibrium positions. Migration occurs when one region is perceived to be superior to the other on the basis of its earnings and amenity levels. Equilibrium is achieved when population movements between the regions eliminate any differences in their relative attractiveness. A comparative-static analysis of the model is presented to analyze the effects of policy changes and exogenous shocks on the distribution of population among the regions." The geographical focus is on the United States.