What is PCIe (Peripheral Component Interconnect Express)?
PCI Express - Wikipedia
What is PCI Express? Do PCIe lanes, slots, and versions matter?
Shuttle announces its Mini-PC (3-liter) with PCI-Express 3.0 x16 slot
Amazon.com: PCIe to PCI Adapter Card,PCI Express x1 to PCI Single/Double Converter,PCI-e Extender Card with USB3.0 Cable for Desktop Sound Card (PCIe to Single PCI Slot) : Electronics
What does PCI Express x16 look like and why is there the number 16? - Quora