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: Women who had undergone pelvic radiotherapy also had a higher risk ( crude relative risk = 7 . 8 , p = 0 . 0001 ) .
### Output Text:
Women who had undergone pelvic radiotherapy also had a higher risk ( crude relative risk = 7 . 8 , p = 0 . 0001 ) . 