«Unit of electric current (ampere).». Oficina Internacional de Pesas y Medidas. Consultado el 19 de agosto de 2013. «The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 x 10–7 newton per metre of length.»
