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: Eight glaucomatous patients chronically treated with timolol 0 . 5 % / 12h , suffering from depression diagnosed through DMS - III - R criteria , were included in the study .
### Output Text:
Eight glaucomatous patients chronically treated with <span class="chemical">timolol</span> 0 . 5 % / 12h , suffering from depression diagnosed through DMS - III - R criteria , were included in the study . 