USA, National Bureau of Standards, Standard yearbook: 1927-[1933], 1932, p. 106 ([Internet, 2016-09-05](https://books.google.ch/books?id=zNYqAQAAIAAJ&pg=PA106&lpg=PA106&dq=%22verification+of+instruments+of+measurement%22&source=bl&ots=Er6PxQFbLi&sig=ME2DlseC3ZwEWLXTeaDQ8zXJiOI&hl=de&sa=X&ved=0ahUKEwijhPG28_fOAhUK1hQKHYpADLUQ6AEIIzAA#v=onepage&q=%22verification%20of%20instruments%20of%20measurement%22&f=false))