Hierarchy of Logical Operators

Operators have their hierarchy If you require more than one operator for one search statement the NOT- and AND-operator receives highest priority at STN, followed by the OR-operator. Every host has its own hierarchy of logical operators. If more operators are to be combined for one search, use always brackets, since bracketed commands are dealt with first. 

Each search step will be marked with a step number, for STN it is an L-number (label number). These numbers help to reaccess former search steps  

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