In trading on Friday, shares of the Vanguard Extended Duration Treasury ETF (EDV) entered into oversold territory, changing hands as low as $99.42 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 Vanguard Extended Duration Treasury, the RSI reading has hit 29.3 — by comparison, the RSI reading for the S&P 500 is currently 40.1. A bullish investor could look at EDV's 29.3 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), EDV's low point in its 52 week range is $99.42 per share, with $138.53 as the 52 week high point — that compares with a last trade of $99.78. Vanguard Extended Duration Treasury shares are currently trading down about 1.4% on the day.