This package, based on txfonts, provides many fixes and enhancements to the txfonts package, splitting it into two separate packages---newtxtext and newtxmath, which may be run independently of one another. It provides scaling, improved metrics, and other options. In particular, newtxmath offers a libertine option which substitutes Linux Libertine (provided with TeXLive and MikTeX) italic and Greek letters for the default Times letters, providing a good match for the Libertine text font, which is heavier than Computer Modern but lighter than Times, and in my experience, looks very sharp and clear on the screen.

Current version: 1.07

This material is subject to the LaTeX Project Public License. See http://www.ctan.org/tex-archive/help/Catalogue/licenses.lppl.html for the details of that license.

Changes in version 1.07:
Added italic small caps font, with and without oldstyle figures, to newtxtext. Fixed some obscure errors in the accompanying fd files.

Changes in version 1.06:
Added code to add option garamondx to newtxmath. (Requires package garamondx from CTAN, non-free.)

Changes in version 1.05:
A number of the changes here were due to valued feedback from Volodya Shavrukov.
0. As of this version, it is required that you install libertine-type1, which serves as a replacement for libertine-legacy. Note too that the map file name has changed to newtx.map from ntx.map.
1. Fixed some remaining references to libertine-legacy fonts so they point now to the included fonts.
2. Added a new option largelibfigs to [libertine]{newtxmath}, changing the figures used in math mode from the default Libertine figures, which are about 8% shorter than Libertine's CapHeight, to Libertine .cap figures, which are exactly match Libertine CapHeight. (The .cap figures in semibold weight required for math bold were created to match the regular style.) 
3. The included fonts zxlr.pfb and zxlz.pfb (used only for math) were updated to include .cap figures.
4. Additional metric changes in ntxmi, ntxmi1 and ntxmia.
5. New OMS symbol virtual fonts tailored for used with the libertine option in newtxmath.
6. Corrected a number of scaling issues due to incorrect macros.
7. Added a new macro \equalht to newtxmath.sty. Applicable only within libertine, with largelibfigs options, making argument set digits and letters to same height.

Change in version 1.042:
1. Changed name libertine-nu.tfm to Libertine-nu.tfm, as it always should have been.

Changes in version 1.041:
1. Fixed ntx[b]mia.{tfm,vf} so they no longer refer to libertine-legacy.

Changes in version 1.04:
1. Adds separate stripped down versions of the Libertine-Legacy fonts (just the parts used in math) so that it is not necessary to install the now obsolete Libertine-legacy package. (The package libertine.sty now points to libertine-type1, its replacement.)
2. Adds a more distinctive nu, activated with the altnu option.
3. The 7pt and 5pt versions of libertine math have been overhauled and are more spread out than former versions. Upright numbers have been added to the math fonts for better rendering in scriptstyle and scriptscriptstyle and more adjustable spacing.
4. Because there are a great many changes in this version, the chance of error is rather high, but the basic functionality is there for the libertine option.
5. IMPORTANT NOTE for TeX Live users: the name of the main map file for this package has been changed to newtx.map from ntx.map. Make sure that there is no copy of the latter in your texmf trees. If you write

kpsewhich ntx.map

and do not get a blank response, you should manually remove the file and update your lsR database.
Changes in version 1.03:
1. Copied parentheses from Times and Libertine Roman txt fonts into ntxmia so that better spacing could be applied in math mode. (The text glyphs are very narrow.)
2. Modified spacing in 7pt and 5pt Libertine math fonts to remove extraneous right side-bearings.
Changes in version 1.02:
1. Additions to newtxtext to provide better superior figures, principally used for footnote and endnote markers.
2. Corrected an encoding error in the 7pt and 5pt math symbol fonts, ntxsy7 and ntxsy5, that prevented display of some glyphs (eg, \langle, \rangle) in subscripts.
Changes in version 1.01:
1. Many minor adjustments to metrics.
2. Added new option libaltvw to newtxmath, which, in libertine math mode, substitutes v and w math italic glyphs manufactured using FontForge, starting from the Libertine upsilon glyphs.
Changes in version 1.00:
1. Added option minion to newtxmath, allowing those possessing a recent basic version of MinionPro to use its Latin and Greek letters to replace the corresponding letters in math mode. (Version 2 or later of MinionPro-Regular.otf, MinionPro-Bold.otf, MinionPro-It.otf and MinionPro-BoldIt.otf required.) Using this option requires installation of the package minion2newtx.
2. Corrected issue with height of accents in bold versions.
3. Added a fix, perhaps temporary, for bad Libertine Italic Theta in fxlri.pfb.
4. Revised ntx.map---needs to be enabled if never previously enabled, or rerun updmap[-sys] to register changes.

Changes in version 0.99
1. Main change is to correct faulty Libertine 5 and 7 pt math fonts distributed with version 0.98.
2. More corrections to sty file and to metrics.

Changes in version 0.98:
1. Many metric changes in bold and regular weights of Libertine Greek glyphs used in newtxmath.
2. Reworked the cmintegrals option to newtxmath and fixed the alphabets loaded by the bold Libertine version.
3. The updated newtxmath seems to be compatible with the recent XeLaTeX and LuaLaTeX.

Changes in version 0.97:
Many metric refinements to the libertine option in newtxmath. The bold math version now works much better though the math accents in bold are somewhat problematic (closer than desirable to the glyphs) because Libertine declares its x-height in semibold and bold to be considerably greater than the actual x-heights, presumably for the benefit of characters that are accented by traditional (OT1) means. The effect is that math accents are lowered substantially. The only option for the math version may be to construct a virtual font without the raised x-height---Ugh.

Changes in version 0.96:
Adds the 40 font support files (.tfm, .vf, .fd) that implement the osf option in newtxtext.sty.

Changes in version 0.95:
1. Copied (virtually) a number of useful glyphs from {\tt symbolsC} to {\tt lettersA} in an effort to reduce the number of mathgroups, which comes perilously close to exceeding 16.
2. Added option nosymbolsc to newtxmath that allows you to not load symbolsC, gaining a mathgroup.
3. Added macro \ShowMathFonts to newtxmath, allowing you to track the mathgroups in use at any stage of the manuscript.
4. Copied (virtually) the STIX Blackboard Bold letters into lettersA in order to give more options for \mathbb without increasing the number of mathgroups, and added the option vvarbb to make it the default target for \mathbb.
5. Expanded documentation, especially concerning mathgroups.
6. The macros \coloneq and \eqcolon now point to the correct glyphs.
7. A number of changes to math font metrics.

Changes in version 0.94:
1. Replaced upright italic glyphs in {\tt lettersA} by their Libertine equivalents, under the option libertine to newtxmath.
2. Fixes to documentation and to my error in libertinealt.enc---thanks are due to Petri Lievonen for picking this up.
3. Added option varbb to newtxmath to force the use of the variant BB alphabet.

Changes in version 0.93:
1. Added optical weights in math italic and math symbol fonts to improve rendering at small sizes.
2. Changed the Linux Libertine math bold weight to their semibold (z) math italics and Greek.
3. Commented out the old txfonts method for square roots---it did not space out as well as laTeX's method.
4. Improved a number of math font metrics.


Installation: Note that any existing ntx.map must be disabled before installation.

Mac OS X: To install, open a Terminal window and cd to inside the downloaded TDS folder.

Method A (recommended): type

sudo cp -Rfp * /usr/local/texlive/texmf-local

then

sudo mktexlsr

then

sudo -H updmap-sys --enable Map=newtx.map

Method B: If you insist on making your font installations in your home folder, potentially making your personal installation become out of sync with updates to TeXLive, use instead

(i) if you checked Update for All Users in TeXLive utility

cp -Rfp * ~/Library/texmf

then

updmap --enable Map=newtx.map

(ii) otherwise

cp -Rfp * ~/Library/texmf

then

sudo updmap-sys --enable Map=newtx.map

Linux: Very similar to Mac OS X.

MikTeX: Copy the newtx.tds.zip to the root of the folder you use for personal additions to the TeX trees, open a command window, chdir to that folder, and type

unzip newtx.tds
initexmf --update-fndb
initexmf --edit-config-file updmap

The latter command should open updmap.cfg in your default editor, commonly Notepad. Add the line 

Map newtx.map 

to updmap.cfg, save and close. Then, in the command window, type

initexmf --mkmaps

You can ignore error messages that may occur here. This should result in a properly enabled newtx.

The underlying glyphs from txfonts are good, and I believe I've improved the metrics and the package substantially. 

Please send comments and bug reports or suggestions for improvement to

msharpe at ucsd dot edu