MOSCOW - Russia has sent anti-aircraft systems to Belarus in retaliation against the delivery to Poland of US-made F-16 warplanes, a source in the Moscow-led Commonwealth of Independent States (CIS) said on Friday. ?Anticipating the arrival of the F-16s in Poland, Russia has sent to Belarus four S-300 anti-aircraft systems which have already been put into service,? according to a source at the headquarters of the anti-aircraft defence alliance of the CIS, quoted by the Itar-Tass news agency. The CIS is made up of the former members of the Soviet Union less the three Baltic states. The alliance was set...