Many doubts surround this issue. Who should be as the 1st, 2nd. 3rd.... co-author on the sequence in a paper? who generated the idea or who worked harder on the paper writting. And if some authors worked more focused on the theoretical background, hypotesis and research framework and other ones on the data collection and analysis?
So, all of those questions come up on the moment when you have to establish the co-authors sequence.
What do you think that should it be the most fair and correct sequence of co-authors in an article?