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: Ten patients with PD and prominent dyskinesias had rTMS ( 1 , 800 pulses ; 1 Hz rate ) delivered over the motor cortex for 4 consecutive days twice , once real stimuli and once sham stimulation were used ; evaluations were done at the baseline and 1 day after the end of each of the treatment series .
### Output Text:
Ten patients with PD and prominent dyskinesias had rTMS ( 1 , 800 pulses ; 1 Hz rate ) delivered over the motor cortex for 4 consecutive days twice , once real stimuli and once sham stimulation were used ; evaluations were done at the baseline and 1 day after the end of each of the treatment series . 