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: The weakness in these patients is due to pathology at both the neuromuscular junction ( most likely due to ND - NMBA ) and muscle ( most likely due to corticosteroids ) .
### Output Text:
The weakness in these patients is due to pathology at both the neuromuscular junction ( most likely due to <span class="chemical">ND - NMBA</span> ) and muscle ( most likely due to <span class="chemical">corticosteroids</span> ) . 