Searches for the H dibaryon and the pentaquark

The pentaquark is described as a doublet of states: $P0=|c̄suud〉$ and $P−=|c̄sddu〉.$ The H dibaryon is described as: $H=|uuddss〉.$ Both were predicted to be stable against strong decay or slightly unbound resonances. The considerations leading to these expectations are reviewed. The main properties of these particles: masses, decay modes, lifetimes and hadroproduction cross sections are discussed. Experimental efforts to search for these particles are reviewed.