Multidimensional economic indicators and multivariate functional principal component analysis (MFPCA) in a comparative study of countries' competitiveness. - Miroslaw Krzysko; Peter Nijkamp; Waldemar Ratajczak; Waldemar Wolynski (J. Geogr. Syst., 2022)

A novel Spatio-temporal principal component analysis based on Geary's contiguity ratio. - Miroslaw Krzysko; Peter Nijkamp; Waldemar Ratajczak; Waldemar Wolynski; Andrzej Wojtyla; Beata Wenerska (Comput. Environ. Urban Syst., 2023)

Economic hierarchical spatial systems - new properties of Löschian numbers. - Jerzy Kaczorowski; Waldemar Ratajczak; Peter Nijkamp; Krzysztof Górnisiewicz (Appl. Math. Comput., 2024)