def validateRefs(cmodel):
    """Validate references for models and layers.

    Args:
        cmodel (dict): Sub-dictionary from config for specific model.

    Returns:
        tuple: (modelrefs, longrefs, shortrefs) where:
            * modelrefs: dictionary of citation information for model
                keys='longref', 'shortref'
            * shortrefs: dictionary containing short reference for each
                input layer
            * longrefs: dictionary containing full references for each
                input layer

    """
    longrefs = {}
    shortrefs = {}
    modelrefs = {}
    for key in cmodel['layers'].keys():
        if 'longref' in cmodel['layers'][key]:
            longrefs[key] = cmodel['layers'][key]['longref']
        else:
            print('No longref provided for layer %s' % key)
            longrefs[key] = 'unknown'
        if 'shortref' in cmodel['layers'][key]:
            shortrefs[key] = cmodel['layers'][key]['shortref']
        else:
            print('No shortref provided for layer %s' % key)
            shortrefs[key] = 'unknown'
    try:
        modelrefs['longref'] = cmodel['longref']
    except BaseException:
        print('No model longref provided')
        modelrefs['longref'] = 'unknown'
    try:
        modelrefs['shortref'] = cmodel['shortref']
    except BaseException:
        print('No model shortref provided')
        modelrefs['shortref'] = 'unknown'
    return modelrefs, longrefs, shortrefs