Convert a list of canonical DOIs to a list of DOIs URLs.

    :param dois: List of canonical DOIs. Can also be a single canonical DOI.
    :returns: A list of DOIs URLs (resp. a single value).

    >>> to_url(['10.1209/0295-5075/111/40005'])
    ['http://dx.doi.org/10.1209/0295-5075/111/40005']

    >>> to_url('10.1209/0295-5075/111/40005')
    'http://dx.doi.org/10.1209/0295-5075/111/40005'

def to_url(dois):
    """
    Convert a list of canonical DOIs to a list of DOIs URLs.

    :param dois: List of canonical DOIs. Can also be a single canonical DOI.
    :returns: A list of DOIs URLs (resp. a single value).

    >>> to_url(['10.1209/0295-5075/111/40005'])
    ['http://dx.doi.org/10.1209/0295-5075/111/40005']

    >>> to_url('10.1209/0295-5075/111/40005')
    'http://dx.doi.org/10.1209/0295-5075/111/40005'
    """
    if isinstance(dois, list):
        return [DX_URL.format(doi=doi) for doi in dois]
    else:
        return DX_URL.format(doi=dois)