Subnet Masks - Snom Service Hub - Snom Service Hub
VLSM Design - Network-Helper
What is Variable Length Subnet Mask (VLSM)?
The TCP/IP Guide - IP Variable Length Subnet Masking (VLSM)
Subnet Mask Cheat Sheet - The Cisco Learning Network
Netmask Quick Reference Chart
You are designing a subnet mask for the 172.26.0.0 network. You want 26 subnets with up to 1800 hosts on each subnet. What subnet mask should you use? - Quora
A supernetwork Comparison of subnet default and supernet