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: MATERIAL AND METHOD : Thirty women ( aged 30 - 77 years ) diagnosed as having OAB at the Gynecology Clinic , King Chulalongkorn Memorial Hospital from January to April 2004 were included in the present study .
### Output Text:
MATERIAL AND METHOD : Thirty women ( aged 30 - 77 years ) diagnosed as having OAB at the Gynecology Clinic , King Chulalongkorn Memorial Hospital from January to April 2004 were included in the present study . 