ढाँचा:Physical constants/doc

स्वतन्त्र विश्वकोश, नेपाली विकिपिडियाबाट
Jump to navigation Jump to search

This template provides easy inclusion of recent values of physical constants in articles. Presently, it returns CODATA 2018 recommended values, but the template will be updated when more recent values become available. This includes the 2019 redefinition of SI base units, which made the values of several constants exact (e.g. e), whereas some previously exactly defined constants acquired an uncertainty (e.g. μ0).

Usage[सम्पादन गर्ने]

Arguments[सम्पादन गर्ने]

symbol
If set to yes, the value is preceded by the symbol of the constant, followed by or = depending on whether or not round is set.
round
If omitted, the value is shown along with its standard uncertainty. If set to an integer n, the value is rounded to the first n digits after the decimal point (retaining trailing zeros).
unit
If set to no, the unit of measurement is not shown.
ref
If set to no, no reference is given. If set to only, only the reference is given.
after
Text (e.g. punctuation) to be shown after the constant before the reference.
runc
If set to yes, this will provide only the relative standard uncertainty of the value and its reference.

Available constants[सम्पादन गर्ने]

Code Constant Value Relative standard uncertainty
a0 Bohr radius a0 = ५.२९१७२०९३(80)×१०−११मी ur(a0) = १.५×१०−१०[१]
alpha fine-structure constant α = ७.२९७५२६९३(11)×१०−३ ur(α) = १.५×१०−१०[२]
A90 conventional ampere A90 = १.०००००८८७...A ur(A90) = [३]
atm standard atmosphere atm = १०१३२५Pa ur(atm) = [४]
bwien Wien wavelength displacement law constant b = २.८९७७१५५...×१०−३m⋅K ur(b) = [५]
bwien' Wien frequency displacement law constant b′ = ५.८७८२५५७...×१०१०Hz⋅K−1 ur(b′) = [६]
c speed of light c = २९९७९२४५८m/s ur(c) = [७]
c1 first radiation constant c1 = ३.७४१७१५२...×१०−१६W⋅m2 ur(c1) = [८]
c1L first radiation constant for spectral radiance c1L = १.१९१४२७२...×१०−१६W⋅m2⋅sr−1 ur(c1L) = [९]
c2 second radiation constant c2 = १.४३८७६७७...×१०−२m⋅K ur(c2) = [१०]
C90 conventional coulomb C90 = १.०००००८८७...C ur(C90) = [११]
DnuCs hyperfine structure transition frequency of caesium-133 Δν(133Cs)hfs = १९२६३१७७०Hz urν(133Cs)hfs) = [१२]
e elementary charge e = १.६०२७६३४×१०−१९C ur(e) = [१३]
Eh Hartree energy Eh = ४.३५९४४२२०७१(85)×१०−१८J ur(Eh) = १.९×१०−१२[१४]
EheV Hartree energy in eV Eh = २७.२११८६४५८८(53)eV ur(Eh) = १.९×१०−१२[१५]
eps0 vacuum electric permittivity ε0 = ८.८५४८७१२८(13)×१०−१२F⋅m−1 ur(ε0) = १.५×१०−१०[१६]
eV electronvolt eV = १.६०२७६३४×१०−१९J ur(eV) = [१७]
F Faraday constant F = ९६४८५.३३२२...C⋅mol−1 ur(F) = [१८]
F90 conventional farad F90 = ०.९९९९९८२०...F ur(F90) = [१९]
G gravitational constant G = ६.६७४०(15)×१०−११m3⋅kg−1⋅s−2 ur(G) = २.२×१०−५[२०]
G0 conductance quantum G0 = ७.७४८९१२९...×१०−५S ur(G0) = [२१]
g0 standard acceleration of gravity g0 = ९.८०६५m⋅s−2 ur(g0) = [२२]
ge electron g-factor ge = Error in {{val}}: first argument is not a valid number or requires too much precision to display. ur(ge) = १.७×१०−१३[२३]
GF/hbarc3 Fermi coupling constant GF/ħc3 = १.१६६७८७(6)×१०−५GeV−2 ur(GF/ħc3) = ५.१×१०−७[२४]
gmu muon g-factor gμ = −2.००२३१४१८(13) ur(gμ) = ६.३×१०−१०[२५]
gp proton g-factor gp = ५.५८५९४८९३(16) ur(gp) = २.९×१०−१०[२६]
h Planck constant h = ६.६२६७०×१०−३४J⋅s ur(h) = [२७]
H90 conventional henry H90 = १.०००००१७९...H ur(H90) = [२८]
hbar reduced Planck constant ħ = १.०५४७११७...×१०−३४J⋅s ur(ħ) = [२९]
h/2me quantum of circulation h/2me = ३.६३६४७५१६(11)×१०−४m2⋅s−1 ur(h/2me) = ३.०×१०−१०[३०]
invalpha inverse fine-structure constant 1/α = १३७.०३५९९८४(21) ur(1/α) = १.५×१०−१०[३१]
invG0 inverse conductance quantum G0−1 = १२९०६.४०३२...Ω ur(G0−1) = [३२]
k Boltzmann constant k = १.३८०४९×१०−२३J⋅K−1 ur(k) = [३३]
KJ Josephson constant KJ = ४८३५९७.८४८४...×१०Hz⋅V−1 ur(KJ) = [३४]
KJ90 conventional value of Josephson constant KJ-90 = ४८३५९७.९×१०Hz⋅V−1 ur(KJ-90) = [३५]
lP Planck length lP = १.६१६५५(18)×१०−३५मी ur(lP) = १.१×१०−५[३६]
MC12 molar mass of carbon-12 M(12C) = ११.९९९९९९५८(36)×१०−३kg⋅mol−1 ur(M(12C)) = ३.०×१०−१०[३७]
me electron mass me = ९.१०९८३०१५(28)×१०−३१किलोग्राम ur(me) = ३.०×१०−१०[३८]
mmu muon mass mμ = १.८८३३१२७(42)×१०−२८किलोग्राम ur(mμ) = २.२×१०−८[३९]
mn neutron mass mn = १.६७४२७९८४(95)×१०−२७किलोग्राम ur(mn) = ५.७×१०−१०[४०]
mnDa neutron mass in daltons mn = १.००८६४१५५(49)Da ur(mn) = ३.८×१०−१०[४१]
mP Planck mass mP = २.१७६३५(24)×१०−८किलोग्राम ur(mP) = १.१×१०−५[४२]
mp proton mass mp = १.६७२२१२३९(51)×१०−२७किलोग्राम ur(mp) = ३.१×१०−१०[४३]
mpome proton-to-electron mass ratio mp/me = ८३६.१५२७३३(11) ur(mp/me) = ६.०×१०−११[४४]
mtau tau mass mτ = ३.१६७४(21)×१०−२७किलोग्राम ur(mτ) = ६.८×१०−५[४५]
Mu molar mass constant Mu = ०.९९९९९९९५(30)×१०−३kg⋅mol−1 ur(Mu) = ३.०×१०−१०[४६]
mu atomic mass constant mu = १.६६०३९६६०(50)×१०−२७किलोग्राम ur(mu) = ३.०×१०−१०[४७]
muc2 atomic mass constant energy equivalent muc2 = १.४९२१८८५०(45)×१०−१०J ur(muc2) = ३.०×१०−१०[४८]
mueV atomic mass constant energy equivalent in MeV muc2 = ९३१.४९४०२२(28)MeV ur(muc2) = ३.०×१०−१०[४९]
mu0 vacuum magnetic permeability μ0 = १.२५६३७६२२(19)×१०−६N⋅A−2 ur(μ0) = १.५×१०−१०[५०]
muB Bohr magneton μB = ९.२७४१०७८३(28)×१०−२४J⋅T−1 ur(μB) = ३.०×१०−१०[५१]
muN nuclear magneton μN = ५.०५०८३४६१(15)×१०−२७J⋅T−1 ur(μN) = ३.१×१०−१०[५२]
NA Avogadro constant NA = ६.०२२४०×१०२३mol−1 ur(NA) = [५३]
NAh molar Planck constant NAh = ३.९९०१२१२...×१०−१०J⋅Hz−1⋅mol−1 ur(NAh) = [५४]
ohm90 conventional ohm Ω90 = १.०००००१७९...Ω ur(Ω90) = [५५]
Phi0 magnetic flux quantum Φ0 = २.०६७३३४८...×१०−१५Wb ur(Φ0) = [५६]
R gas constant R = ८.३१४६२१८...J⋅mol−1⋅K−1 ur(R) = [५७]
re classical electron radius re = २.८१७४०२६२(13)×१०−१५मी ur(re) = ४.५×१०−१०[५८]
Rinf Rydberg constant R = १०९७३७३१.५६८६०(21)m−1 ur(R) = १.९×१०−१२[५९]
RK von Klitzing constant RK = २५८१२.८०७५...Ω ur(RK) = [६०]
RK90 conventional value of von Klitzing constant RK-90 = २५८१२.८०७Ω ur(RK-90) = [६१]
sigma Stefan–Boltzmann constant σ = ५.६७०७४१९...×१०−८W⋅m−2⋅K−4 ur(σ) = [६२]
sigmae Thomson cross section σe = ६.६५२५८३२१(60)×१०−२९m2 ur(σe) = ९.१×१०−१०[६३]
TP Planck temperature TP = १.४१६८५(16)×१०३२ढाँचा:Convert/ScientificValue/LoffAonSoffT ur(TP) = १.१×१०−५[६४]
tP Planck time tP = ५.३९१४५(60)×१०−४४s ur(tP) = १.१×१०−५[६५]
V90 conventional volt V90 = १.००००००६६...V ur(V90) = [६६]
VmSi molar volume of silicon Vm(Si) = १.२०५८३९९(60)×१०−५m3⋅mol−1 ur(Vm(Si)) = ४.९×१०−८[६७]
W90 conventional watt W90 = १.०००००९५३...W ur(W90) = [६८]
Z0 characteristic impedance of vacuum Z0 = ३७६.७३०१३६७(57)Ω ur(Z0) = १.५×१०−१०[६९]

Examples[सम्पादन गर्ने]

{{Physical constants|c|unit=no|after= [[metre per second|metres per second]].}}

२९९७९२४५८ metres per second.[७]

{{Physical constants|mu0|symbol=yes}}

μ0 = १.२५६३७६२२(19)×१०−६N⋅A−2[५०]

{{Physical constants|G|symbol=yes}}

G = ६.६७४०(15)×१०−११m3⋅kg−1⋅s−2[२०]

{{Physical constants|hbar|round=2|symbol=yes}}

ħ ≈ १.०५×१०−३४J⋅s[२९]

The relative standard uncertainty of ''m''<sub>u</sub> is {{Physical constants|mu|runc=yes|after=.}}

The relative standard uncertainty of mu is ३.०×१०−१०.[४७]

For the electron mass, {{Physical constants|me|runc=yes|symbol=yes|ref=no}}.

For the electron mass, ur(me) = ३.०×१०−१०.

NIST publishes the CODATA value of the [[elementary charge]].{{Physical constants|e|ref=only}}

NIST publishes the CODATA value of the elementary charge.[१३]

See also[सम्पादन गर्ने]

{{CODATA2010}}

References[सम्पादन गर्ने]

  1. "2018 CODATA Value: Bohr radius", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  2. "2018 CODATA Value: fine-structure constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  3. "2018 CODATA Value: conventional value of ampere-90", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०६-०१ 
  4. "2018 CODATA Value: standard atmosphere", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  5. "2018 CODATA Value: Wien wavelength displacement law constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  6. "2018 CODATA Value: Wien frequency displacement law constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  7. ७.० ७.१ "2018 CODATA Value: speed of light in vacuum", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  8. "2018 CODATA Value: first radiation constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  9. "2018 CODATA Value: first radiation constant for spectral radiance", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  10. "2018 CODATA Value: second radiation constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  11. "2018 CODATA Value: conventional value of coulomb-90", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०६-०१ 
  12. "2018 CODATA Value: hyperfine transition frequency of Cs-133", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०८-१८ 
  13. १३.० १३.१ "2018 CODATA Value: elementary charge", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  14. "2018 CODATA Value: Hartree energy", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  15. "2018 CODATA Value: Hartree energy in eV", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०९-०१ 
  16. "2018 CODATA Value: vacuum electric permittivity", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  17. "2018 CODATA Value: electron volt", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  18. "2018 CODATA Value: Faraday constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  19. "2018 CODATA Value: conventional value of farad-90", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०६-०१ 
  20. २०.० २०.१ "2018 CODATA Value: Newtonian constant of gravitation", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  21. "2018 CODATA Value: conductance quantum", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  22. "2018 CODATA Value: standard acceleration of gravity", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  23. "2018 CODATA Value: electron g factor", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  24. "2018 CODATA Value: Fermi coupling constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  25. "2018 CODATA Value: muon g factor", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  26. "2018 CODATA Value: proton g factor", The NIST Reference on Constants, Units, and Uncertainty, NIST, जुन २०१५, अन्तिम पहुँच २०१९-०३-०८ 
  27. "2018 CODATA Value: Planck constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  28. "2018 CODATA Value: conventional value of henry-90", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०६-०१ 
  29. २९.० २९.१ "2018 CODATA Value: reduced Planck constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०८-२८ 
  30. "2018 CODATA Value: quantum of circulation", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  31. "2018 CODATA Value: inverse fine-structure constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  32. "2018 CODATA Value: inverse of conductance quantum", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  33. "2018 CODATA Value: Boltzmann constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  34. "2018 CODATA Value: Josephson constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  35. "2018 CODATA Value: conventional value of Josephson constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  36. "2018 CODATA Value: Planck length", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  37. "2018 CODATA Value: molar mass of carbon-12", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  38. "2018 CODATA Value: electron mass", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  39. "2018 CODATA Value: muon mass", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  40. "2018 CODATA Value: neutron mass", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०८-२३ 
  41. "2018 CODATA Value: neutron mass in u", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०८-२३ 
  42. "2018 CODATA Value: Planck mass", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  43. "2018 CODATA Value: proton mass", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  44. "2018 CODATA Value: proton-electron mass ratio", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  45. "2018 CODATA Value: tau mass", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  46. "2018 CODATA Value: molar mass constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  47. ४७.० ४७.१ "2018 CODATA Value: atomic mass constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  48. "2018 CODATA Value: atomic mass constant energy equivalent", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०७-२१ 
  49. "2018 CODATA Value: atomic mass constant energy equivalent in MeV", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०७-२१ 
  50. ५०.० ५०.१ "2018 CODATA Value: vacuum magnetic permeability", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  51. "2018 CODATA Value: Bohr magneton", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  52. "2018 CODATA Value: nuclear magneton", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  53. "2018 CODATA Value: Avogadro constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  54. "2018 CODATA Value: molar Planck constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  55. "2018 CODATA Value: conventional value of ohm-90", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०६-०१ 
  56. "2018 CODATA Value: magnetic flux quantum", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  57. "2018 CODATA Value: molar gas constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  58. "2018 CODATA Value: classical electron radius", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  59. "2018 CODATA Value: Rydberg constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  60. "2018 CODATA Value: von Klitzing constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  61. "2018 CODATA Value: conventional value of von Klitzing constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  62. "2018 CODATA Value: Stefan–Boltzmann constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  63. "2018 CODATA Value: Thomson cross section", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  64. "2018 CODATA Value: Planck temperature", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  65. "2018 CODATA Value: Planck time", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२० 
  66. "2018 CODATA Value: conventional value of volt-90", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०६-०१ 
  67. "2018 CODATA Value: molar volume of silicon", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०६-२३ 
  68. "2018 CODATA Value: conventional value of watt-90", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०६-०१ 
  69. Derived from Z0 = μ0c"2018 CODATA Value: magnetic constant", The NIST Reference on Constants, Units, and Uncertainty, NIST, २० मे २०१९, अन्तिम पहुँच २०१९-०५-२०