diff --git a/src/Find.jl b/src/Find.jl
index c09e53c..0448128 100644
--- a/src/Find.jl
+++ b/src/Find.jl
@@ -1,14 +1,42 @@
 """
-# module Find
+    findvolume(form, eos, y, x, method)
 
+Calculate volumes based on crude eos and input pressures
 
+#Arguments
+- `form::EquationForm`: an `EquationForm` instance. If `EnergyForm`, fit ``E(V)``; if `PressureForm`, fit ``P(V)``; if `BulkModulusForm`, fit ``B(V)``.
+- `eos::EquationOfState`: a trial equation of state.
+- `y::Real`: a real number of pressure value.
+- `x0::Union{AbstractVector,Tuple}`: an AbstractVector or Tuple of volume range.
+- `method <:AbstractUnivariateZeroMethod`: a method used to do calculation.
 
 # Examples
 
 ```jldoctest
-julia>
-```
-"""
+
+    # Data in the following tests are from
+    # https://github.com/materialsproject/pymatgen/blob/1f0957b8525ddc7d12ea348a19caecebe6c7ff34/pymatgen/analysis/tests/test_eos.py
+
+julia>pressures = collect(0:20:200) .* u"GPa"
+julia>eos = BirchMurnaghan3rd(167u"angstrom^3", 2600u"kbar", 4.0u"1000mm/m")
+julia>volumes = map(
+        p -> findvolume(PressureForm(), eos, p, (eps() * u"bohr^3", eos.v0 * 1.3)),
+        pressures,
+    )
+
+11-element Array{Quantity{Float64,�^3,Unitful.FreeUnits{(Å^3,),�^3,nothing}},1}:
+167.0 Å^3
+156.14036210727835 Å^3
+147.99803635986558 Å^3
+141.5109371379587 Å^3
+136.13864615965332 Å^3
+131.5678403193935 Å^3
+127.60046278645824 Å^3
+124.10332447387113 Å^3
+120.9825768060646 Å^3
+118.16962836248427 Å^3
+115.61284838696815 Å^3
+"""sf
 module Find
 
 using InteractiveUtils: subtypes