| Keyword | Most frequent expressions (number of websites) |
|---|---|
| hf | delta hf (3), hf turbo (2), hf integrale (2), hf tegellijm (1), table hf (1), hf mic (1), failure hf (1), hf educational (1), analysis hf (1), hf optimum (1), restrictive hf (1), website hf (1), hf contest (1) |