In trading on Friday, shares of the iShares S&P GSCI ETF (GSG) GSG entered into oversold territory, changing hands as low as $31.52 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of iShares S&P GSCI, the RSI reading has hit 27.7 — by comparison, the RSI reading for the S&P 500 is currently 47.8. A bullish investor could look at GSG's 27.7 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side.Looking at a chart of one year performance (below), GSG's low point in its 52 week range is $28.30 per share, with $35.52 as the 52 week high point — that compares with a last trade of $31.52. iShares S&P GSCI shares are currently trading off about 1.1% on the day.