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: Each combination was associated with significantly greater reductions in MSSBP and MSDBP compared with the monotherapies and placebo ( all , P < 0 . 001 ) .
### Output Text:
Each combination was associated with significantly greater reductions in MSSBP and MSDBP compared with the monotherapies and placebo ( all , P < 0 . 001 ) . 