A Raman detecting system for detecting a vapor of an explosive includes a surface-enhanced Raman scattering substrate for absorbing the vapor of the explosive. The crosslinking agent includes a copolymer having at least 30 mol % of alternating structural units of a residue from a donor monomer and a residue from one or more acrylic acceptor monomers. The phase-shifting mask is suitable for testing the effect of lights of two wavelengths on a layer of photoresist. The lesson completion record is immediately transmitted upon completion of the lesson to a student andor an education authority in order to certify that the student has completed the lesson and has spent the requisite minimum time period on that lesson. The buckle is very strongly pulled, and the webbing is set at a third belt tension. A clearance subsystem confirms the integrity of both the messages and their delivery and ensures that each message is delivered once and intact.