I realized something strange when searching on Scopus' database.
If I query some words in the field "TITLE-ABS-KEY", I do not get the same results as if I query each field individually, separated by "OR"s.
For example, the query:
TITLE-ABS-KEY ( flood mitigation dam river OR stream )
finds 163 papers.
Whereas the query:
TITLE ( flood mitigation dam river OR stream )
OR ABS ( flood mitigation dam river OR stream )
OR KEY ( flood mitigation dam river OR stream )
finds only 140 papers.
Does anyone know if this is to be expected, and if so, what is the difference between both queries?