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 AND METHODS : The randomized sample consisted of 234 euthymic men who were receiving some type of SSRI .
### Output Text:
PATIENTS AND METHODS : The randomized sample consisted of 234 euthymic men who were receiving some type of <span class="chemical">SSRI</span> . 