The aerodynamic characteristics of airfoils at negative angles of attack
A 1932 NASA technical report from the NACA series presenting wind-tunnel test results for airfoils at negative angles of attack, written for aeronautical engineers. Its pictures are rotated engineering graphs plotting lift, drag, pitching moment and centre of pressure against angle of attack, with small airfoil cross-section outlines beside each curve set. A designer might take from them the clean graph conventions of dual labelled axes, dashed and solid curve styles and tiny airfoil profile diagrams.
