这本书是有关于地磁的.This book is about the earth's magnetism.他们发现, 牛在吃草或是休息的时候, 总是面向地磁的南极或是北极.And, when grazing or resting, cows tended to face either magnetic north or south....
I am writing with reference to your article on salaries for scientists.我写此信是为了回应你那篇探讨科学家薪水的文章。He summed up his philosophy, with reference to Calvin.他总结了自己的哲学，还提及了加尔文。We can quantify these contributions with reference to ...