# selector-combinator-allowed-list Specify a list of allowed combinators. ```css a + b {} /** ↑ * This combinator */ ``` This rule normalizes the whitespace descendant combinator to be a single space. This rule ignores [reference combinators](https://www.w3.org/TR/selectors4/#idref-combinators) e.g. `/for/`. ## Options `array|string`: `["array", "of", "combinators"]|"combinator"` Given: ``` [">", " "] ``` The following patterns are considered violations: ```css a + b {} ``` ```css a ~ b {} ``` The following patterns are _not_ considered violations: ```css a > b {} ``` ```css a b {} ``` ```css a b {} ```