Radiographic Exposure
Delmars Principles of Radiologic Imaging
An Art and a Science
Author:  Richard R. Carlton and Arlene M. Adler

General Positioning
Merrill's Atlas of Radiographic Positions & Radiologic Procedures, 11th Edition
Authors: Phillip W. Ballinger and Eugene D. Frank

Delmars Principles of Radiographic Positioning & Procedures Pocket Guide
Authors:  Richard R. Carlton, Joanne S. Greathouse, Arlene Adler, and Ray Winters