PS: Survey
Source 1: http:// www. nawcinc. com / wmfaq. html
S2: http:// www. worldbookonline. com / student / article? id = ar458550 & st = clo ud-seeding
S3: http:// www. 2facts. com / icof _ story. aspx? PIN = i1500140 & term = cloud + seedi ng + saudi + arabia
S4: http:// www. reference. com / browse / wiki / Silver _ iodide
S5: http:// science. howstuffworks. com / nature / climateweather / meteorologists / cloud-seeding1. htm
S6: http:// www. scientificamerican. com / article. cfm? id = cloud-seedingchina-snow
S7: http:// archives. smdailyjournal. com / article _ preview. php? id = 121045
S8: http:// reason. org / blog / show / deaths-from-hurricanes-floods-droug
S9: http:// www. chacha. com / question / how-many-people-die-per-yeardue-to-food-shortage