Snowflake Certification Guide: Boost Your Data Warehousing Skills
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sicara.fr
This is a reasonable guide to the study resources available. I'd also point out that there was an O'Reilly book released relatively recently that's currently available for free from the Snowflake website: https://resources.snowflake.com/ebooks/snowflake-definitive-...
Adam Morton has also written a book on Snowflake, too.
Both go into much more detail than required for the Core exam, but are comprehensive and will give you all the information you need for Core and much of the Advanced exam contents.