August is reminding investors that the stock market can actually sell off after or during a bull market that is now over six years old. Still, the one trend that has held up for almost four years is that every pullback has been followed by a rally to new highs. Now it seems that many investors are starting to turn to value stocks after many of the key growth stocks have risen so much.

24/7 Wall St. reviews dozens of analyst reports and research reports each day to find some of those overlooked value calls for investors. When it comes to stocks to buy, some analyst reports get very aggressive with upside of 50% to 100% or more — way over the traditional 8% to 15% upside calls for most Dow and S&P 500 analyst ratings.

Investors need to understand that the higher the implied upside there is, there are almost certainly more caveats and risks to consider. 24/7 Wall St. tracked some of these analyst calls with massive upside seen in just the past week. We found six standout analyst calls with upside of over 50% in companies that many or most investors may know.

Eldorado Gold

Eldorado Gold Corp. (NYSE: EGO) faces the same issues as other gold exploration and production outfits by relying on gold for its lifeblood. A late week call from BMO Capital Markets brought an analyst upgrade, to Outperform from Market Perform. The firm also raised its target to $7.00 from $5.00, implying upside of almost 80% from the $3.92 close on Friday (and even higher than the $3.81 prior close).

If you want a more conservative view, earlier in the week RBC Capital Markets maintained its Outperform rating but trimmed its target to $5.50 from $6.50. Eldorado made an announcement of favorable rulings from the Greek government over its forestry land and site clearing rights at its project in Halkidiki.

ALSO READ: 6 Oil and Energy Stocks Analysts Want You to Buy Now

Yahoo

Yahoo! Inc. (NASDAQ: YHOO) is a home run for investors, if the analyst team at Sanford Bernstein is correct. The firm came out and raised Yahoo to Outperform from Market Perform on Thursday, issuing a massive upside price target of $52.00. Shares were at $34.49 prior to this key upgrade, implying upside of 51%.

Yahoo shares went out on Friday at $36.24, so investors may be paying attention. Despite the weakness in Alibaba and despite the criticism of many others regarding the core business, Bernstein’s sum of the parts view is that just about every last bit of downside and bad news is priced into the stock now. Yahoo has a consensus analyst target price of about $51 and a 52-week trading range of $33.85 to $52.62.

Yelp

Yelp Inc. (NYSE: YELP) finally may have found a rekindled friendship. Shares of the reviews site were reiterated as Outperform at Credit Suisse on Wednesday. What stands out here is the Credit Suisse $44 price target. Yelp had closed at $25.35 prior to the call, and shares went out at $25.77 on Friday. This implies upside of 70%.

Yelp’s consensus target price has bled down to $34.50 or so, and it has a 52-week range of $23.66 to $86.88. The buyout hopes may be gone here, but Credit Suisse sees Yelp as a property that is undermonetized and now likes its long-term investment thesis after management meetings.

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Aspen Aerogels

Aspen Aerogels Inc. (NYSE: ASPN) was recently highlighted in the six energy stocks analysts want you to buy, but this tiny $165 million market cap outfit is an energy technology company that uses aerogel insulation for many key refining, petrochemical, LNG and subsea operations. Global Hunter started coverage mid-week with a Buy rating and a $13.00 price target. That was against a $6.85 prior close and a $7.20 close on Friday.

Aspen Aerogels has a 52-week range of $6.21 to $11.14. Even at the higher closing price, it still has some 80% implied upside if the Global Hunter assessment is correct. Its consensus price target from seven analysts is $10.93, with its highest analyst target is up at $14.00 and the lowest is $8.00. In a different view, Needham assigned a Buy rating ahead of Global Hunter with a more conservative price target of $9.50.