In 1897 the United States leads the world in the following ratios: Tons Pig Iron. Edward W. Byrn.十九世纪发明进展.
Since the real difference is so slight, we can assume the simpler ratios without appreciable error. 伯莎M.克拉克.科学通论.
Improved clutches, gear ratios which permit varying speeds, double-braking systems and electric lights are present-day refinements which add zest to the sport of motorcycling. 佚名.神奇的知识之书.