Missing "factor" property in code example
7.3.4 Physical types and units: Code 9. More examples for defining units the "factor" property is missing in the following line of the code example:
...
unit |foot/s| of speed is SI(m: 1, s: -1, 0.3048)
...
should be corrected to:
...
unit |foot/s| of speed is SI(m: 1, s: -1, factor: 0.3048)
...