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: At six months post - CAB , patients with severe anemia had a Hb mean value of 10 . 2 + / - 0 . 1 g / dl ( X + / - SE ) , whereas the other patients had mild anemia with Hb mean value of 13 . 2 + / - 0 . 17 ( X + / - SE ) .
### Output Text:
At six months post - CAB , patients with severe anemia had a Hb mean value of 10 . 2 + / - 0 . 1 g / dl ( X + / - SE ) , whereas the other patients had mild anemia with Hb mean value of 13 . 2 + / - 0 . 17 ( X + / - SE ) . 