The IEEE doi needs https://doi.org added to 10.1109/TE.1987.5570523 before adding the TXSTATE proxy url
https://libproxy.txstate.edu/login?url=https://doi.org/10.1109/TE.1987.5570523
DOI Example:
On a PC, if you right-click over the DOI it does add the https://doi.org to the DOI. Otherwise, you can just copy/paste the DOI as it displays on the record and add https://doi.org manually.