Even though we recommend careful selection and validation of reference genes for each assay and cell line, any of YWHAZ, TBP, PPIA, and EF1A1 or their combination (we recommend at least two) could be used as starting reference genes in assays of osteoblastic differentiation when using other types of osteosarcoma cells or cell lines. Here, EEF1A1 is linked to osteosarcoma.