The following articles cover a lot of information about reserves, reserve studies and reserve funding:
The Importance of Regular Reserve Fund Assessments
Step-by-Step Reserve Study Guidelines for Homeowners Association Budgets
Breaking Down What Goes into a Homeowners Association Reserve Fund
What Can HOA Reserve Funds Be Used For?
Homeowners Association Reserve Study: Examining Your Association’s Financial Health
Understanding the Differences Between a New Building Reserve Fully Funded vs Threshold Funded