See showpdb.txt, select structureid="h1" (for helix 1), etc.

METHODS:

http://wiki.jmol.org/index.php/Protein_Community#Secondary_structure

Where default is DSSP 2.0.
Alpha carbon only models: method of Levitt & Greer (link to doi).

VERSIONS:

Jmol vs Authors: version 2.8, May 2019.


IMPLEMENTATION:

	makeRocketSpt() in scripts.js
	makeRocketHelp() in help.js

	secondaryStructureToggle() scripts.js

STATE VARIABLES:

These two variables appear to be redundant:
  rocketMode is a (authors) or j (jmol).
  secondaryStructureIs = a (authors) or j (jmol).

jmol: helixsheetrecords (string with records, length 0 if none).
javascript: authorsHelixSheet t/f.