3 literature references for Parus inornatus sequestratus (Grinnell & Swarth, 1926):

Author:
Year: 1996
Title:
Source: database, NODC Taxonomic Code
Author: American Ornithologists' Union
Year: 1957
Title:
Source: Check-list of North American Birds, 5th Edition
Author: Cicero, Carla
Year: 2000
Title: Oak Titmouse (Baeolophus inornatus) and Juniper Titmouse (Baeolophus ridgwayi)
Source: The Birds of North America, no. 485