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"
"exogenous estrogen sulfide" » "exogenous estrogens sulfide", "exogenous hydrogen sulfide", "exogenous dinitrogen sulfide", "exogenous nitrogen disulfide"
"exogenous nitrogen sulfide" » "exogenous estrogens sulfide", "exogenous latrogenic sulfide", "exogenous androgens sulfide", "exogenous dinitrogen sulfide", "exogenous nitrogen disulfide", "exogenous hydrogen sulfide"

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 ((("exogenous estrogen sulfide") OR ("exogenous nitrogen sulfide"))))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"endogenous estrogen sulfide\") or (((\"exogenous estrogen sulfide\") OR (\"exogenous nitrogen sulfide\"))))*".
• Removing quotes may allow a broader search: (( endogenous estrogen sulfide ) or ((( exogenous estrogen sulfide ) OR ( exogenous nitrogen sulfide ))))*.