# What year did NHL referees stop wearing name plates and change to numbers on their sweaters?

This practise of wearing numbers only was started in the 1994/95 NHL season.

### Should FIFA provide more on field security for referees?

I think this should definitely be considered. Thankfully, there haven't been any serious incidents involving referees at senior level, but all it takes is one unsavoury character to change all that. On the negative side, the costs may be considered to high to employ greater security at high profile games.

### Why are the use of numbers in formulae discouraged?

Because if the numbers change then you have to change the formula. Numbers commonly change in spreadsheets. You should put the numbers into cells and then refer to the cell in the formula. If the number in the cell changes, then the formula will be able to work without having to be changed, as it will use whatever value is in the cell.

### Does addition and subtraction of vectors obey the commutative law?

Addition does. Subtraction, just as with numbers: a - b is not equal to b - a, but you can change a - b to -b + a. Addition does. Subtraction, just as with numbers: a - b is not equal to b - a, but you can change a - b to -b + a. Addition does. Subtraction, just as with numbers: a - b is not equal to b - a, but you…