from typing import List


def clean_authors(authors_list: List[str], sign: str) -> List[str]:
    """
    Cleans a list of author names by splliting them based on a given sign.

    Args: 
        authors_list (:obj:`List[str]`):
            A list of author names.
        sign (:obj:`str`):
            Sign that separates author names in the list.

    Returns:
        :obj:`List[str]`:
            A list of splitted author names.
    """
    if authors_list:
        authors = list()
        for author in authors_list:
            if sign in author:
                authors.extend([name.strip() for name in author.split(sign)])
            else:
                authors.append(author)
        return authors
    return authors_list