When it comes to building a winning stock portfolio, it's often helpful to study the strategies of successful investors and incorporate them into your personal stock-buying game plan. I often quote Warren Buffett's sage advice in my articles and firmly believe that investors of all trading styles and ages can glean wisdom from his long-term value-oriented investing philosophy.

If you want to add some Buffett-approved stocks to your portfolio this month, you've come to the right place. Today, we're going to look at two top stocks owned by Buffett's Berkshire Hathaway (NYSE:BRK.A) (NYSE:BRK.B) that long-term investors shouldn't hesitate to scoop up right now.

Let's dive right in.

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1. Snowflake

Cloud-based data storage company Snowflake (NYSE:SNOW) made quite a splash when it debuted as a publicly traded entity last September. The company's initial public offering (IPO) was priced at $120 per share, but by early December, the stock was trading at just shy of $400. Shares have retracted notably since then. The stock is trading down about 8% year to date, although it's worth noting that it's still up by more than 6% from its IPO roughly 10 months ago.

One of the core tenets of Buffett's investing philosophy is to buy shares of quality companies that are undervalued by the broader market and have strong competitive advantages to drive durable, long-term growth. Snowflake's volatility in recent months has discouraged some investors, but it's important to remember that share price alone doesn't indicate whether a stock is a quality buy.

Snowflake is a key player in the global data-warehousing market. In fact, Snowflake controls a whopping 16.3% percent share of this fast-growing industry. Allied Market Research reports that the data warehousing market achieved a valuation of $21.2 billion in 2019, and is on track to hit a global valuation of more than $51 billion as of the year 2028.

Now, let's look at Snowflake's financials. The company ended its fiscal 2021 on Jan. 31. During the 12-month period, Snowflake reported product revenue that was up 120% to reach $553.8 million. It also generated a stellar product gross profit margin of 65% for the full year.

The company certainly didn't disappoint when it reported its financial results for the first quarter of its fiscal 2022 on May 26. During the three-month period, product revenue shot up 110% year over year. In addition, it delivered a healthy product gross profit margin of 66% for the quarter.

Also notable was the fact that Snowflake's net revenue retention rate -- which indicates recurring streams of revenue from existing customers in a trailing-two-year period – had soared to 168% as of the end of the quarter. The company closed the quarter with 4,532 customers, a 67% spike from the year-ago period, and $1.4 billion of remaining performance obligations (customer orders yet to be fulfilled), a year-over-year increase of 206%.

When a company is growing as fast as Snowflake, it's natural to wonder how it's doing in terms of liquidity. The good news is, the business closed the first quarter of its fiscal 2022 with about $645 million in cash and cash equivalents, $3.3 billion in short-term investments, and total assets of $5.9 billion. In contrast, it has about $777 million in total current liabilities, which are obligations due within the next year.

Meanwhile, the company is targeting between 88% and 92% in year-over-year product revenue growth for the second quarter, while expecting its fiscal 2022 product revenue growth to be in the ballpark of 84% to 87%.

Even with Snowflake's share price volatility in recent months, analysts still estimate that the stock has a potential upside of more than 100%. The company is likely to continue experiencing some immediate growing pains as it expands its business and global footprint within the rapidly evolving data warehousing industry, but patient investors could reap serious portfolio rewards from this high-growth stock over the long term.

2. Bristol Myers Squibb

When it comes to healthcare stock stalwarts, few can compete with Bristol Myers Squibb's (NYSE:BMY) track record. The company has been in business since 1887, and is one of the top pharmaceutical companies in the world. 

Shares of Bristol Myers Squibb have continued to rise slowly but steadily following the market crash of March 2020. The stock is trading approximately 15% higher than just one year ago, and is up about 11% year to date.

For full-year 2020, Bristol Myers reported 63% revenue growth for a total of $42.5 billion. And in the first quarter of 2021, the company's total revenue rose 3% year over year, with U.S. revenue alone jumping 4%. It also reported a gross profit margin of 74.3% for the three-month period.

The company owes its sustained balance-sheet growth to its extensive range of top-selling biopharmaceutical products, which were boosted by its November 2019 acquisition of Celgene and its purchase of heart disease specialist MyoKardia in November 2020.

Cancer drug Revlimid (acquired from Celgene), blood-thinner Eliquis, immunotherapy treatment Opdivo, psoriatic arthritis drug Orencia, multiple myeloma treatment Pomalyst (acquired from Celgene), chemotherapy drug Sprycel, and melanoma drug Yervoy were the top products driving Bristol Myers' balance sheet gains in the most recent quarter. Revlimid and Eliquis alone raked in total product revenue of about $2.9 billion each.

The company's pipeline currently features over 50 compounds in development across more than three dozen therapeutic areas. Management is forecasting high-single-digit revenue growth for the full year, while analysts are predicting that the company can deliver similar average annual earnings growth for the upcoming five-year period.

Investors should also know that the blue chip stock pays a nice dividend that yields just shy of 3% at the time of this writing. (The average stock in the S&P 500 pays a dividend of less than 2%.) The company has a solid track record of yearly dividend increases. Last December, management announced a 9% hike to its quarterly dividend.

If you're looking for steady share price growth, a robust balance sheet fortified by an impressive lineup of blockbuster drugs, and an attractive dividend, Bristol Myers Squibb is a no-brainer buy to add to your basket today and hold forever. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.