How to attach K-1s for Composite Returns

My partnership files composit returns for all partners in about 10 states where we are non-residents. We are only provided K-1s for thoses states. When I added the credit for those states to my California return, the program said that I had to attach copies of the returns, which I assume means the K-1s. Can I attach those K-1s to an electronically filed return, or do I have to send a paper return?

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