While the literature on second language acquisition and use is overwhelmingly rich with respect to initial and intermediate stages of development, present knowledge of levels of ultimate attainment that are equal or close to that if native speakers has so far not been presented in a coherent manner. This is what the present volume aims to achieve. In addition to chapters that summarize what is currently known about the grammatical, lexical, and discourse features that continue to exhibit instability at the most advanced levels of second language development, the volume presents overviews of...