BALLOU, DONALD H.
Plane trigonometry, by Donald H. Ballou & Frederick H. Steen.
BALLOU, DONALD H. Plane trigonometry, by Donald H. Ballou & Frederick H. Steen. © 18May43; A175651. Donald H. Ballou & Frederick H. Steen (A); 20May70; R484979.
Donald H. Ballou & Frederick H. Steen|A