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: Based on these data , it can be speculated that pubertal AAS users with low central 5 - HT may be especially prone to exhibit aggressive behavior .
### Output Text:
Based on these data , it can be speculated that pubertal AAS users with low central <span class="chemical">5 - HT</span> may be especially prone to exhibit aggressive behavior . 