Articles? Try papers. It was so much of a shit-show that it's become the standard case study of how to not expand to other countries. And the failure goes well beyond how they treated employees, it all starts by trying to compete with Aldi and Lidl on their home turf, saying "we'll have lower prices" while also trying to "convince the German customer with great service", which of course costs money. And Germans don't want people to pack their groceries that costs money.
They also ignored laws left and right, again not just when it comes to employment (e.g. trying to forbid that employees date each other) but also more general, say, having loss leaders: In Germany, you can't sell products below the wholesale price you paid yourself. You can sell it at zero profits, but not at a loss (unless, say, it's ice cream and your refrigerator just failed). Other strategic mistakes include buying up stores from a German chain that failed because it had shit store locations.
That's not to say that you can't export how you do things to other countries -- case in point, Aldi: They started to become big in the US after the financial crisis but Aldi Süd opened their first store in the US in 1976. They stayed small, grew organically, meanwhile learning how Americans tick, what products they like, where they're willing to buy store-brand and where not (e.g. store-brand toothpaste is a non-starter), and learned how to talk to Americans, how to explain why things are done like Aldi does them. And, TBH, "Don't waste your grocery money on a bagger" is easier to sell than the opposite.
And they don't have much issue convincing people that their store brand stuff is good, it's generally produced according to EU standards. Like the bread containing sourdough instead of a chemical cocktail, and chocolate that's, no, not stellar, but not full of cheap non-cocoa fats. Meanwhile, Wallmart was selling duvet covers that didn't fit any blankets or pillows any German had. Figures that standard sizes differ between countries and you should pay attention to such stuff.
They also have insanely high employee retention for US standards, and aren't unionised -- They aren't unionised in Germany, either, which is only to like 5% up to Aldi fighting it actively, the rest is their, for lack of better word, paternalistic company culture: You don't become manager at Aldi without having swept floors, stocked shelves, and sat at the register, and even when you're a manager that's still what you do, just not while there's paperwork that has to be dealt with. That's not standard US corporate culture -- but it pretty much is world-wide small owner-run store culture: Everyone does everything, as needed, and bosses wield mops. It's a busy work day every day but the pay is good, drama is minimal, and the employer is loyal to you.