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  1. string <- 'ABC (2013c), Something Something Text (Volume II): Some more blabla, the usual, end of string'
  2.  
  3. rx <- paste0("\\b(?:[Vv]ol(?:ume)?|Issue|No|Nr|nr|no|Number)\\s*(?:\\d+|V?I{0,3}X?L?C{0,3}D?M?)")
  4. library(stringr)
  5. str_extract_all(string, rx)
Success #stdin #stdout 0.27s 42284KB
stdin
Standard input is empty
stdout
[[1]]
[1] "Volume II"