While the most advanced technology has been used to photograph and reproduce this manuscript, the qualiiy of the reproduction is heavily dependent upon the quality of the material submitted. For example:• Manuscript pages may have indistinct print. In such cases, the best available copy has been filmed.• Manuscripts may not always be complete. In such cases, a note will indicate that it is not possible to obtain missing pages.• Copyrighted material may have been removed from the manuscript. In such cases, a note will indicate the deletion.Oversize materials (e.g., maps, drawings, and charts) are photographed by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each oversize page is also filmed as one exposure and is available, for an additional charge, as a standard 35mm slide or as a 17"x 23" black and white photographic print.Most photographs reproduce acceptably on positive microfilm or microfiche but lack the clarity on xerographic copies made from the microfilm. For an additional charge, 35mm slides of 6"x 9" black and white photographic prints are available for any photographs or illustrations that cannot be reproduced satisfactorily by xerography.