...a classical modular form of weight <img class="inline-math" data-math-type="inline-math" src="data:image/svg+xml;base64,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"/>...In our approach we replace Hirzebuch's smooth complex analytic compactification <img class="inline-math" data-math-type="inline-math" src="data:image/svg+xml;base64,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"/> of the Hilbert modular surface <img class="inline-math" data-math-type="inline-math" src="data:image/svg+xml;base64,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"/>...