https://www.nist.gov/publications/dimensionless-units-si
Dimensionless units in the SI | NIST
Feb 19, 2017 - The International System of Units (SI) is supposed to be coherent.
dimensionless unitsin thenist
https://www.boost.org/doc/libs/1_52_0/doc/html/boost/units/quantity_BOOST_U_id1897170.html
Class template quantityBOOST_UNITS_DIMENSIONLESS_UNIT(System), Y
class templatedimensionless unitunitssystem