iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Install memory in an iMac - Apple Support
iMac Intel 21.5" Retina 4K Display (2017) RAM and SATA Hard Drive Upgrade - iFixit Repair Guide
How to Upgrade the Memory in the iMac Pro (late 2017) - YouTube
Upgrade your iMac 27'' 2017 RAM with MrMemory review - Wim Arys
Upgrade your iMac's RAM in less than 5 minutes - YouTube
Amazon.com: OWC 32GB (4x8GB) 2400MHZ DDR4 SO-DIMM PC4-19200 Memory Upgrade Compatible with 2017 iMac 27 inch with Retina 5K Display (OWC2400DDR4S32S) : Everything Else
Amazon.com: OWC 32GB (2 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S32P) : Everything Else
A-Tech 8GB RAM for Apple iMac 2017 (27 inch Retina 5K & 21.5 inch Retina 4K) | DDR4 2400MHz SODIMM PC4-19200 1.2V 260-Pin SO-DIMM Memory Upgrade Module at Amazon.com