See [here at w3schools](https://www.w3schools.com/cssref/css_selectors.php)

## Matching attributes
```css
a[href]
a[href*="flibble"] { ... }    /* <a> elements whose href contains "flibble" */
a[href^="mr"] { ... }         /* <a> elements whose href begins with "mr" */
a[href$="hexvision"] { ... }  /* <a> elements whose href ends with "hexvision" */
a[href*="://" ] { ... }       /* external links and URIs */
```