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Factor loadings from 4 factor exploratory structural equation model.

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Factor loadings from 5 factor exploratory structural equation model.

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Factor loadings from 6 factor exploratory structural equation model.

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Reliability of the Polish COVID-Stress Scales (CSS-PL) and correlations among the CSS-PL Scales.

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Results from COVID Stress Scale measurement invariance tests across times 1 and 2.

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Results from COVID Stress Scale item response models with parameter constraints across times 1 and 2 supported by DIF tests.

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Tests of discriminant validity: Comparison of the CSS-PL correlations with current anxiety and depression.

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Tests of discriminant validity: Comparison of the mean correlations for distress measures versus correlation with general xenophobia.

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Scree plots for COVID Stress Scales item factor analyses in the Polish and Dutch samples.

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Sample characteristics of the total sample at T1 and T22 and as a function of attrition rate between T1 and T2.