Tag order
Except for the first tag of each reference, which must be "TY  - " and the last tag of each reference, which must be "ER  - ," the tags within each reference can be in any order.

Characters allowed in fields
The characters allowed in the reference ID fields can be in the set "0" through "9," or "A" through "Z." The characters allowed in all other fields can be in the set from "space" (character 32) to character 255 in the IBM Extended Character Set. Note, however, that the asterisk (character 42) is not allowed in the author, keywords or periodical name fields.

How to handle long fields
If the information following any one tag is more than 70 characters long, it is allowable (though not necessary) to insert a carriage return/line feed at the end of 70 characters, and continue on the next line.