WE DEEPLY APPRECIATE the efforts of our colleagues at Wiley and Serendipity23 Editorial Services in bringing this revised fourth edition to fruition. The contributions of our project editor, Adaobi Obi Tulton, whose deft edits, organization, and persistence kept us on track, and the personal attention of our executive editor, Jim Minatel, were especially key, and we thank them for their time, work, and assistance.

The quality of this edition has been greatly improved by the work of our technical editors, Wayne Heym and Dan Hill, both of whom have already made important contributions to prior editions. Their thoughtful comments and meticulous review have eliminated numerous errors and oversights and immeasurably improved the clarity of the book. We thank them for their extensive work. We are also grateful to Andrew Taylor for additional review of the new data science material, and Tom Mongan for assistance with proofreading.

No fourth edition would have been possible without the three that preceded it, and the many people who contributed to them. John is particularly grateful for Michael J. Mongan’s help in facilitating his participation with the third edition. We thank our third edition editor Maureen Spears, who swiftly and surely overcame the unique challenges that arose in preparation of that edition. Additionally, we thank our original editors, Margaret Hendrey and Marjorie Spencer, for their patience and helpfulness. We are also grateful to our original reviewers and advisors, Dan Hill, Elise Lipkowitz, Charity Lu, Rob Maguire, and Tom Mongan. Dan’s contributions in particular were tremendous—the quality of the first edition was vastly improved by his careful and detailed reviews.