Determining Optimal Gear Ratios of a Two-stage Helical Reducer for Getting Minimal Acreage of Cross SectionNguyen Khac Tuan, Vu Ngoc Pi, Nguyen Thi Hong Cam, Tran Thi Phuong Thao, Ho Ky Thanh, Le Xuan Hung and Hoang Thi ThamMATEC Web Conf., 213 (2018) 01008DOI: https://doi.org/10.1051/matecconf/201821301008