Here at Zacks, our focus is on the proven Zacks Rank system, which emphasizes earnings estimates and estimate revisions to find great stocks. Nevertheless, we are always paying attention to the latest value, growth, and momentum trends to underscore strong picks.Of these, perhaps no stock market trend is more popular than value investing, which is a strategy that has proven to be successful in all sorts of market environments. Value investors use fundamental analysis and traditional valuation metrics to find stocks that they believe are being undervalued by the market at large.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.One stock to keep an eye on is Kelly Services (KELYA). KELYA is currently sporting a Zacks Rank of #1 (Strong Buy) and an A for Value. The stock has a Forward P/E ratio of 9.53. This compares to its industry's average Forward P/E of 13.03. Over the last 12 months, KELYA's Forward P/E has been as high as 12.41 and as low as 8.88, with a median of 10.17.Value investors also use the P/S ratio. The P/S ratio is is calculated as price divided by sales. This is a popular metric because sales are harder to manipulate on an income statement, so they are often considered a better performance indicator. KELYA has a P/S ratio of 0.14. This compares to its industry's average P/S of 0.4.Finally, our model also underscores that KELYA has a P/CF ratio of 4.46. 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 9.38. KELYA's P/CF has been as high as 23.60 and as low as 4.05, with a median of 7.33, all within the past year.These are just a handful of the figures considered in Kelly Services's great Value grade. Still, they help show that the stock is likely being undervalued at the moment. Add this to the strength of its earnings outlook, and we can clearly see that KELYA is an impressive value stock right now.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 To read this article on Zacks.com click here.