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: Newborn female Wistar rats were fed a lithium - containing diet ( 50 mmol / kg ) for 8 weeks and then randomized to normal diet , HP diet ( 40 vs . 19 % ) , NX or HP + NX for another 8 weeks .
### Output Text:
Newborn female Wistar rats were fed a <span class="chemical">lithium</span> - containing diet ( 50 mmol / kg ) for 8 weeks and then randomized to normal diet , HP diet ( 40 vs . 19 % ) , NX or HP + NX for another 8 weeks . 