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: In order to identify risk factors associated with the development of hypercalcemia , indirect parameters of intestinal calcium reabsorption and bone turnover rate in these 14 patients were compared with results in 14 eucalcemic patients matched for age , sex , length of time on dialysis , and etiology of renal disease .
### Output Text:
In order to identify risk factors associated with the development of hypercalcemia , indirect parameters of intestinal <span class="chemical">calcium</span> reabsorption and bone turnover rate in these 14 patients were compared with results in 14 eucalcemic patients matched for age , sex , length of time on dialysis , and etiology of renal disease . 