def find_diff_nodes(S,T):
    """Returns a list of nodes that have different formulas in graphs S and T."""
    diff_nodes = []
    for node in S:
        s_formula = S.formula_conj(node)
        t_formula = T.formula_conj(node)
        if s_formula != t_formula:
            diff_nodes.append(node)
    return diff_nodes