While the proven Zacks Rank places an emphasis on earnings estimates and estimate revisions to find strong stocks, we also know that investors tend to develop their own individual strategies. With this in mind, we are always looking at value, growth, and momentum trends to discover great companies.Considering these trends, value investing is clearly one of the most preferred ways to find strong stocks in any type of market. Value investors use a variety of methods, including tried-and-true valuation metrics, to find these stocks.On top of the Zacks Rank, investors can also look at our innovative Style Scores system to find stocks with specific traits. For example, value investors will want to focus on the "Value" category. Stocks with high Zacks Ranks and "A" grades for Value will be some of the highest-quality value stocks on the market today.Petrobras (PBR) is a stock many investors are watching right now. PBR is currently holding a Zacks Rank of #1 (Strong Buy) and a Value grade of A.Investors should also recognize that PBR has a P/B ratio of 0.97. The P/B ratio pits a stock's market value against its book value, which is defined as total assets minus total liabilities. PBR's current P/B looks attractive when compared to its industry's average P/B of 1.19. Over the past year, PBR's P/B has been as high as 1.67 and as low as 0.79, with a median of 1.03.Finally, we should also recognize that PBR has a P/CF ratio of 2.32. This figure highlights a company's operating cash flow and can be used to find firms that are undervalued when considering their impressive cash outlook. This stock's P/CF looks attractive against its industry's average P/CF of 3.72. Over the past 52 weeks, PBR's P/CF has been as high as 10.63 and as low as 2.04, with a median of 3.49.These are only a few of the key metrics included in Petrobras's strong Value grade, but they help show that the stock is likely undervalued right now. When factoring in the strength of its earnings outlook, PBR looks like an impressive value stock at the moment. Time to Invest in Legal Marijuana If you’re looking for big gains, there couldn’t be a better time to get in on a young industry primed to skyrocket from $17.7 billion back in 2019 to an expected $73.6 billion by 2027. After a clean sweep of 6 election referendums in 5 states, pot is now legal in 36 states plus D.C. Federal legalization is expected soon and that could be a still greater bonanza for investors. Even before the latest wave of legalization, Zacks Investment Research has recommended pot stocks that have shot up as high as +285.9%. You’re invited to check out Zacks’ Marijuana Moneymakers: An Investor’s Guide. It features a timely Watch List of pot stocks and ETFs with exceptional growth potential.Today, Download Marijuana Moneymakers FREE >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Petroleo Brasileiro S.A. Petrobras (PBR): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research