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: Lithium is implicated in drug - induced nephrogenic DI , and because the patient had not received lithium since being admitted to the hospital , his treatment changed to focus on nephrogenic DI .
### Output Text:
<span class="chemical">Lithium</span> is implicated in drug - induced nephrogenic DI , and because the patient had not received <span class="chemical">lithium</span> since being admitted to the hospital , his treatment changed to focus on nephrogenic DI . 