Perhaps you should try some spelling variations:
"endogenous estrogen sulfide" » "exogenous estrogens sulfide", "endogenous hydrogen sulfide", "endogenous pyrogen sulfide", "endogenous dinitrogen sulfide", "endogenous nitrogen disulfide"
"endogenous nitrogen sulfide" » "endogenous estrogens sulfide", "endogenous hydrogen sulfide", "endogenous pyrogen sulfide", "endogenous dinitrogen sulfide", "endogenous nitrogen disulfide"
"exogenous estrogen sulfide" » "exogenous estrogens sulfide", "exogenous hydrogen sulfide", "exogenous dinitrogen sulfide", "exogenous nitrogen disulfide"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("endogenous estrogen sulfide") OR ("endogenous nitrogen sulfide"))) OR ("exogenous estrogen sulfide"))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"endogenous estrogen sulfide\") OR (\"endogenous nitrogen sulfide\"))) or (\"exogenous estrogen sulfide\"))*".
• Removing quotes may allow a broader search: (((( endogenous estrogen sulfide ) OR ( endogenous nitrogen sulfide ))) or ( exogenous estrogen sulfide ))*.