def get_mask_names_dict(mask_names, tracer_names):
    """
    Return a dictionary with the mask names assotiated to the fields to be
    correlated

    Parameters:
    -----------
        mask_names (dict):  Dictionary of the masks names assotiated to the
        fields to be correlated. It has to be given as {1: name1, 2: name2, 3:
        name3, 4: name4}, where 12 and 34 are the pair of tracers that go into
        the first and second Cell you are computing the covariance for; i.e.
        <Cell^12 Cell^34>. In fact, the tjpcov.mask_names.
        tracer_names (dict):  Dictionary of the tracer names of the same form
        as mask_name.

    Returns:
    --------
        masks_names_dict (dict):  Dictionary with the mask names assotiated to the
        fields to be correlated.

    """
    mn  = {}
    for i in [1, 2, 3, 4]:
        mn[i] = mask_names[tracer_names[i]]
    return mn