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: Evaluation revealed a hemoglobin of three grams , 3 + Coombs ' test with polyspecific anti - human globulin and monospecific IgG reagents , and a warm reacting autoantibody .
### Output Text:
Evaluation revealed a hemoglobin of three grams , 3 + Coombs ' test with polyspecific anti - human globulin and monospecific IgG reagents , and a warm reacting autoantibody . 