Editorial on writing equations and mathematical expressions: some basic principles.

2. Vectors should be written in lower case bold font, e.g . a and matrices in upper case bold, e.g . A. Other algebraic symbols (except Greek uppercase letters) including parameters and scalar variables should be written in italics. Operators such as log, e, cos and d should be written in regular (and not in italics unlike their associated variables x and y : log x , ex, cos x , dy dx ). Note that e x should normally be used unless the exponent is a complicated function when exp(x ) is acceptable.