In trading on Monday, shares of the iShares S&P North American Natural Resources Sector Index Fund ETF (IGE) entered into oversold territory, changing hands as low as $37.42 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 North American Natural Resources Sector Index Fund, the RSI reading has hit 28.2 — by comparison, the RSI reading for the S&P 500 is currently 52.0. A bullish investor could look at IGE's 28.2 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), IGE's low point in its 52 week range is $33.05 per share, with $41.84 as the 52 week high point — that compares with a last trade of $37.39. iShares S&P North American Natural Resources Sector Index Fund shares are currently trading down about 4.7% on the day.