The angiosperms are the sister phylum to which gymnosperm phylum?

The flowering plants, also known as angiosperms, are similar to gymnosperms which are capable of producing seeds. However they are distinguished from the latter by characteristics which includes flowers, endosperms within the seeds and the production of fruits that contain the seeds. They are the sister phylum to the following four gymnosperm groups namely, the conifers, cycad, gingko and gnetophytes.