Final answer:
Yes, a custom summary formula in Salesforce can reference other summary formulas using the '&' operator.
Step-by-step explanation:
Yes, a custom summary formula in Salesforce can reference other summary formulas using the '&' operator. This allows you to build complex summary formulas that incorporate multiple summary calculations. For example, if you have two summary formulas, 'Sum of A' and 'Sum of B', you can create a third formula that calculates the sum of both by using the syntax 'Sum of A & Sum of B'.
By referencing other summary formulas, you can perform advanced calculations and aggregations on data. This is particularly useful when you need to create cumulative or derived summaries that rely on the results of existing summary formulas.