Your search term replication study returns the following data from GWAS Central:
Phenotype search results:
Search term replication study was not recognised as a MeSH/HPO phenotype term or synonym

Gene/region search results:
Search term replication study was not recognised as a gene or region

Studies search results:
1,000 Studies contain the keyword replication studyView and refine results..

Marker search results:
Search term replication study was not recognised as a marker identifier or identifiers