In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Patients with an adherence to SOP > 70 % were classified into the high adherence group ( HAG ) and patients with an adherence of < 70 % into the low adherence group ( LAG ) .
### Output Text:
Patients with an adherence to SOP > 70 % were classified into the high adherence group ( HAG ) and patients with an adherence of < 70 % into the low adherence group ( LAG ) . 