**Table 1:** JPL DE200 ephemeris of PSR B1937+21 (data from Effelsberg and WSRT observations).
Parameter	Value
Right Ascension (J2000)	$19^{\rm h}$ $39^{\rm m}$ 38 $.\!\!^{\rm s}$ 560096(6)
Declination (J2000)	$21^\circ$ 34' 59 $.\!\!^{\prime\prime}$ 13552(13)
Proper motion in RA (mas yr^-1)	-0.05(2)
Proper motion in Dec (mas yr^-1)	-0.47(4)
Frequency (Hz)	641.928244534462(3)
Frequency derivative (Hz s^-1)	$-4.331046(13)\times 10^{-14}$
Frequency 2nd derivative (Hz s^-2)	$8.9(1.8)\times 10^{-27}$
Epoch of the period (MJD)	52328.0
DM (cm^-3 pc)	71.02666(16)
DM derivative (pc cm^-3 yr^-1)	-2.10(17)
Epoch validity start/end (MJD)	50360 - 52867
Epoch of arrival time $^\dagger$ (MJD)	52332.167314839268(11)
Frequency of arrival time (MHz)	1409.300
Post-fit timing rms (ns)	910

Note: Uncertainties quoted are in the last digit(s) and represent $2\sigma$ estimates (twice the formal TEMPO errors).
The Epoch of arrival time refers to the maximum of the main peak in the integrated radio profile.
$^\dagger$ At Effelsberg telescope.

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