Read this: Literary Catalan allows the use of words from different dialects, except those of very restricted use. However, from the 19th century onwards, there is a tendency of favoring words of Northern dialects in detriment of others, even though nowadays there is a greater freedom of choice.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): What can use words from different dialects?
Literary Catalan