@inbook{1106375273, author={Glenn D. Posner and Jessica Dy and Amanda Black and Griffith D. Jones}, title={Preface}, booktitle={Oxorn-Foote Human Labor & Birth, 6e}, publisher={McGraw-Hill Medical}, address={New York, NY}, year={2015}, url={obgyn.mhmedical.com/content.aspx?aid=1106375273} }