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: These were evaluated with respect to the duration of lithium therapy , age , sex , and family history ( whether or not the patient had a first - degree relative with thyroid disease ) .
### Output Text:
These were evaluated with respect to the duration of <span class="chemical">lithium</span> therapy , age , sex , and family history ( whether or not the patient had a first - degree relative with thyroid disease ) . 