Most older issues are out of print and sold out.
Your best bet would be to try an out of print book search, or purchase a photocopy from Spring. I know that Daimon Verlag, our European distributor has a few copies of Spring from the 70s. Please contact Eliane at for further details and purchasing information. I know it's not much, but I hope my response was somewhat helpful. Please contact me with further questions if you should have any.