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: A higher cumulative incidence of persistent leukocyturia was found in children with an area under the curve > 19 mg / L x h or a peak serum level of indinavir > 12 mg / L .
### Output Text:
A higher cumulative incidence of persistent leukocyturia was found in children with an area under the curve > 19 mg / L x h or a peak serum level of <span class="chemical">indinavir</span> > 12 mg / L . 