In trading on Thursday, shares of the iShares S&P GSCI Commodity-Indexed Trust ETF (GSG) entered into oversold territory, changing hands as low as $26.33 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 Commodity-Indexed Trust, the RSI reading has hit 26.3 — by comparison, the RSI reading for the S&P 500 is currently 65.7. A bullish investor could look at GSG's 26.3 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 $26.33 per share, with $34.33 as the 52 week high point — that compares with a last trade of $26.35. iShares S&P GSCI Commodity-Indexed Trust shares are currently trading down about 2.4% on the day.