def _reference_to_html(reference: tuple[str, str]) -> str:
    """Return HTML element made of a reference tuple i.e. `("bj", "7,9")`."""
    ref_type, ref_id = reference
    # E.g. <a class='bj' id='bj7.2'>BJ 7.2</a>
    return f"<a class='{ref_type}' id='{ref_type}{ref_id}'>{ref_type.upper()} {ref_id}</a>"