Several links that don’t work for a while.
These ones just turn out blank (usually after a few days/weeks i have access):
[https://doi.org/10.1016/j.cvex.2020.08.001](https://doi.org/10.1016/j.cvex.2020.08.001)
[https://doi.org/10.5818/1529-9651-30.2.54](https://doi.org/10.5818/1529-9651-30.2.54)
[https://doi.org/10.5818/19-01-184.1](https://doi.org/10.5818/19-01-184.1)
[https://doi.org/10.5818/19-09-212.1](https://doi.org/10.5818/19-09-212.1)
[https://doi.org/10.1053/j.jepm.2020.12.009](https://doi.org/10.1053/j.jepm.2020.12.009)
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These ones i get other articles, not the ones i’m searching for (an example because they are all from the same journal, last edition):
[https://doi.org/10.1053/j.jepm.2020.12.009](https://doi.org/10.1053/j.jepm.2020.12.009)
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Any ideas for solving these two situations?