SPNE and Pareto Optimality "The SPNE of a sequential game might not necessarily be Pareto Optimal"


I understand the definitons of Nash Equilibria and Pareto Optimality and that these are not synonymous concepts. An example in reference to this question would be a Firm-Union Wage Setting Game, in which there might be $w$ offers which provide greater payoffs to both the firm and union. 
Please share some other examples for the same. Thanks!
Proof of "the SPNE of a sequential game might not necessarily be Pareto Optimal"?
I don't get it, your example is a proof of this statement. So what else do you need?

If you need another example, just take the prisoner's dilemma, and turn into a sequential game with imperfect information. Then, the NE is equal to the SPNE and you have an equilibrium without Pareto optimality