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: METHODS : Thirteen medication - free children with autism ( mean age , 8 . 8 + / - 3 . 5 years ) participated in a 12 - week , open - label trial of galantamine .
### Output Text:
METHODS : Thirteen medication - free children with autism ( mean age , 8 . 8 + / - 3 . 5 years ) participated in a 12 - week , open - label trial of <span class="chemical">galantamine</span> . 