It is the most preferred choice of editing. It looks intensively on the format, structure, meaning, tense, point of view and clarifying meaning and sig...
Copyediting includes Grammar, Spelling, Punctuation, Syntax error, format correction. Editing on the other hand, refers to revision and reorganization ...
You should assign letters to each citation to distinguish them for the readers. For an instance: (Walter, 2001a) (Walter, 2001b) (Walter, 2001c).