Changes in version 3.1                         

    o   3.1.3: added link to psd to satisfy CRAN error

    o   CI is handled via Github Actions (replaces Travis-CI)

    o   3.1.2: Fixed error in vignette engine specification

    o   3.1.1: added a ticks.only option to logticks

    o   3.1: Added the model of Wang et al (2018;
	10.1029/2018WR022793), to the model toolbox and to the
	ResponseModels toolbox. Thanks to @jkennel for contributing
	this.

    o   New test validating Wang model against Hsieh model (they are
	equivalent when specific leakage is zero).  Thanks to @jkennel
	for contributing this.

    o   Previous build on CRAN broke because sapa/ifultools were
	removed; hence, the specifics of cross_spectrum have changed.
	The code now uses new functionality from the CRAN package.
	(sapa/ifultools were unreliablely maintained for a while.)  One
	benefit is this new approach allows for adaptive refinement of
	the (sine-multitaper) cross spectrum rather than uniform
	tapering across all frequencies. But, one unfortunate
	consequence is that any codes/scripts using the Welch option
	(i.e., k=NULL) will break.

                         Changes in version 2.3                         

    o   Fixes a sign error in the Liu solution. Thanks to @jkennel for
	catching this.

    o   Removed the need for pandoc-citeproc in Tohoku vignette because
	of a presently unfixed bug.

                 Changes in version 2.2-2 (2018-09-14)                  

    o   NA values stop execution of cross_spectrum; and, added tests.

    o   NEW FUNCTION: logsmoo which can be used to smooth hdr signals
	in log-space

    o   UPDATED: Tohoku cross-spectrum vignette

    o   Added DOIs for references

                        Changes in version 2.2-1                        

    o   Added optional switch to cross_spectrum to switch from
	multitaper to Welch overlapping estimation

                        Changes in version 2.2-0                        

    o   Tohoku cross-spectrum vignette

    o   Function for cross-spectrum computation

    o   Includes Windows CI via AppVeyor

    o   unit-testing framework (testthat, CRAN), with some tests

                        Changes in version 2.1-1                        

    o   Mostly a maintenance release.

    o   Travis-CI is now used to track builds; see also the github
	page.

                 Changes in version 2.1-0 (2013-10-04)                  

    o   New capability to model open well response: open_well_response

    o   well_response now returns complex frequency response only,
	rather than returnin amplitude and phase as separate vectors.

    o   Substantial documentation improvements (and shuffling around).

    o   Response functions now add attributes and class to output:
	'wrsp' and 'owrsp' for sealed and open well response,
	respectively.

    o   New methods for 'wrsp' and 'owrsp', including plot.wrsp, for
	example.

    o   kitplot is simply a link to plot.wrsp

    o   Changed variable names in well_response and added defaults in
	case some are missing.

    o   Added a vignette highlighting model differences.

    o   New utility function .in0to1 to test for existence between zero
	to one; this is useful to check if a parameter is valid (e.g.
	Skemptons ratio).

    o   New utility constants to access stored physical constants.

                 Changes in version 1.1-1 (2013-03-12)                  

    o   Removed empty .Last.lib function.

    o   Added missing closures in 'NEWS.Rd'.

                        Changes in version 1.1-0                        

    o   Added .onAttach message into 'zzz.R' file.

    o   NEWS is now in Rd format in the inst/ directory.

                 Changes in version 1.0-1 (2012-10-26)                  

    o   This marks the first release to CRAN.

    o   added a demo

    o   bug fix: when given a single frequency (omega), the calculation
	failed

    o   documentation improved

                        Changes in version 1.0-0                        

    o   First version, checks ok.

    o   Documentation complete, thanks to roxygen2 (CRAN).