Litecoin.watch (2026-10-15). One signed transaction, or another payment?. Version: Core 0.21.5.8 · release 2026-10-15.1. https://litecoin.watch/articles/how-to-avoid-paying-twice-with-litecoin Method and data: https://litecoin.watch/uploads/research/duplicate-payments-20261015-v1/README.txt