For advanced search the following operators can be used:
" * " matches the full or partial term (e.g.: term* )
" + " filter the results (e.g.:  term1  +term2 )
" - " disregard the results containing that term (e.g.:  term1  -term2)
" < " lowers the relevance of the specified term (e.g.:  term1  )
" > " raises the relevance of the specified term (e.g.:  term1  >term2)
" ~ " lowers the relevance of the specified term and lists the results at the bottom of the list (e.g.:  term1  ~term2)
" ( ) " group terms for a more complex search (e.g.:  term1  +(term2 term3) )