Anal Biochem. 2010 Feb 15;397(2):227-32. doi:10.1016/j.ab.2009.10.022

Pinto FL, Lindblad P.

A guide for in-house design of template-switch-based 5' rapid amplification of cDNA ends systems.

Uses desoxyriboguanosine tails for template switching (but the last one is blocked by a propyl group (C3 spacer).