diff --git a/README.md b/README.md
index 096cd1a..d1e6f90 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@ This project is licensed under the terms of the Apache License 2.0.
 Augmented Dickey-Fuller test:
 
 ```rust
-use unit_root::prelude::distrib::AlphaLevel;
+use unit_root::prelude::distrib::{AlphaLevel,Regression};
 use unit_root::prelude::nalgebra::DVector;
 use unit_root::prelude::*;
 
@@ -42,13 +42,16 @@ fn main() {
     let lag = 2;
     
     // compute the test statistic
-    let report = tools::adf::constant_no_trend_test(&y, lag).unwrap();
-    
+    let regression = Regression::Constant;
+    let report = tools::adf::adf_test(&y, lag, regression).unwrap();
+
     // critical values for the model with a constant but no trend:
-    let critical_value = distrib::dickeyfuller::constant_no_trend_critical_value(
+    let critical_value = distrib::dickeyfuller::get_critical_value(
+        regression,
         report.size,
         AlphaLevel::OnePercent,
-    );
+    )
+    .unwrap();
     assert_eq!(report.size, 10);
 
     // comparison
diff --git a/benches/adf.rs b/benches/adf.rs
index 03e236d..a209ec5 100644
--- a/benches/adf.rs
+++ b/benches/adf.rs
@@ -16,7 +16,8 @@
 #![allow(missing_docs)]
 use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};
 use rand::SeedableRng;
-use unit_root::prelude::tools::adf;
+use unit_root::prelude::distrib::Regression;
+use unit_root::prelude::tools::adf::adf_test;
 use unit_root::utils::gen_ar_1;
 
 fn adf_benchmark_f32_2(c: &mut Criterion) {
@@ -30,7 +31,7 @@ fn adf_benchmark_f32_2(c: &mut Criterion) {
         let y = gen_ar_1(&mut rng, *size, mu, delta, sigma);
 
         c.bench_with_input(BenchmarkId::new("adf_f32_2", size), &y, |b, y| {
-            b.iter(|| adf::constant_no_trend_test(y, lag))
+            b.iter(|| adf_test(y, lag, Regression::Constant))
         });
     }
 }
@@ -46,7 +47,7 @@ fn adf_benchmark_f64_2(c: &mut Criterion) {
         let y = gen_ar_1(&mut rng, *size, mu, delta, sigma);
 
         c.bench_with_input(BenchmarkId::new("adf_f64_2", size), &y, |b, y| {
-            b.iter(|| adf::constant_no_trend_test(y, lag))
+            b.iter(|| adf_test(y, lag, Regression::Constant))
         });
     }
 }
@@ -62,7 +63,7 @@ fn adf_benchmark_f32_10(c: &mut Criterion) {
         let y = gen_ar_1(&mut rng, *size, mu, delta, sigma);
 
         c.bench_with_input(BenchmarkId::new("adf_f32_10", size), &y, |b, y| {
-            b.iter(|| adf::constant_no_trend_test(y, lag))
+            b.iter(|| adf_test(y, lag, Regression::Constant))
         });
     }
 }
@@ -78,7 +79,7 @@ fn adf_benchmark_f64_10(c: &mut Criterion) {
         let y = gen_ar_1(&mut rng, *size, mu, delta, sigma);
 
         c.bench_with_input(BenchmarkId::new("adf_f64_10", size), &y, |b, y| {
-            b.iter(|| adf::constant_no_trend_test(y, lag))
+            b.iter(|| adf_test(y, lag, Regression::Constant))
         });
     }
 }
diff --git a/benches/dickeyfuller.rs b/benches/dickeyfuller.rs
index 7217368..9ea3345 100644
--- a/benches/dickeyfuller.rs
+++ b/benches/dickeyfuller.rs
@@ -16,6 +16,7 @@
 #![allow(missing_docs)]
 use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};
 use rand::SeedableRng;
+use unit_root::prelude::distrib::Regression;
 use unit_root::prelude::tools::dickeyfuller;
 use unit_root::utils::gen_ar_1;
 
@@ -29,7 +30,7 @@ fn df_benchmark_f32(c: &mut Criterion) {
         let y = gen_ar_1(&mut rng, *size, mu, delta, sigma);
 
         c.bench_with_input(BenchmarkId::new("df_f32", size), &y, |b, y| {
-            b.iter(|| dickeyfuller::constant_no_trend_test(y))
+            b.iter(|| dickeyfuller::dickeyfuller_test(y, Regression::Constant))
         });
     }
 }
@@ -44,7 +45,7 @@ fn df_benchmark_f64(c: &mut Criterion) {
         let y = gen_ar_1(&mut rng, *size, mu, delta, sigma);
 
         c.bench_with_input(BenchmarkId::new("df_f64", size), &y, |b, y| {
-            b.iter(|| dickeyfuller::constant_no_trend_test(y))
+            b.iter(|| dickeyfuller::dickeyfuller_test(y, Regression::Constant))
         });
     }
 }
diff --git a/examples/adf.rs b/examples/adf.rs
index 57e6b64..9b1dd2f 100644
--- a/examples/adf.rs
+++ b/examples/adf.rs
@@ -13,7 +13,7 @@
 // limitations under the License.
 
 //! Example of the Augmented Dickey-Fuller test
-use unit_root::prelude::distrib::AlphaLevel;
+use unit_root::prelude::distrib::{AlphaLevel, Regression};
 use unit_root::prelude::nalgebra::DVector;
 use unit_root::prelude::*;
 
@@ -34,14 +34,13 @@ fn main() {
 
     // compute the test statistic
     let lag = 1;
-    let report = tools::adf::constant_no_trend_test(&y, lag).unwrap();
+    let regression = Regression::Constant;
+    let report = tools::adf::adf_test(&y, lag, regression).unwrap();
 
     // critical values for the model with a constant but no trend:
-    let critical_value = distrib::dickeyfuller::constant_no_trend_critical_value(
-        report.size,
-        AlphaLevel::OnePercent,
-    )
-    .unwrap();
+    let critical_value =
+        distrib::dickeyfuller::get_critical_value(regression, report.size, AlphaLevel::OnePercent)
+            .unwrap();
     assert_eq!(report.size, 9);
 
     // comparison
diff --git a/examples/dickeyfuller.rs b/examples/dickeyfuller.rs
index 1c9181a..51ac134 100644
--- a/examples/dickeyfuller.rs
+++ b/examples/dickeyfuller.rs
@@ -14,7 +14,7 @@
 
 //! A simple example of how to use the library
 use unit_root::prelude::distrib::dickeyfuller::constant_no_trend_critical_value;
-use unit_root::prelude::distrib::AlphaLevel;
+use unit_root::prelude::distrib::{AlphaLevel, Regression};
 use unit_root::prelude::nalgebra::DVector;
 use unit_root::prelude::*;
 
@@ -33,7 +33,7 @@ fn main() {
         -0.42968979,
     ]);
 
-    let report = tools::dickeyfuller::constant_no_trend_test(&y).unwrap();
+    let report = tools::dickeyfuller::dickeyfuller_test(&y, Regression::Constant).unwrap();
 
     let critical_value =
         constant_no_trend_critical_value(report.size, AlphaLevel::OnePercent).unwrap();
diff --git a/src/lib.rs b/src/lib.rs
index 9458cbf..7f51910 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -17,9 +17,10 @@
 //! # Examples
 //!
 //! ```rust
-//! use unit_root::prelude::distrib::dickeyfuller::constant_no_trend_critical_value;
-//! use unit_root::prelude::distrib::AlphaLevel;
+//! use unit_root::prelude::distrib::dickeyfuller::get_critical_value;
+//! use unit_root::prelude::distrib::{AlphaLevel, Regression};
 //! use unit_root::prelude::nalgebra::DVector;
+//! use unit_root::prelude::tools::adf::adf_test;
 //! use unit_root::prelude::*;
 //!
 //! let y = DVector::from_row_slice(&[
@@ -37,10 +38,11 @@
 //! ]);
 //!
 //! let lag = 2;
-//! let report = tools::adf::constant_no_trend_test(&y, lag).unwrap();
+//! let regression = Regression::Constant;
+//! let report = adf_test(&y, lag, regression).unwrap();
 //!
 //! let critical_value: f64 =
-//!     constant_no_trend_critical_value(report.size, AlphaLevel::OnePercent).unwrap();
+//!     get_critical_value(regression, report.size, AlphaLevel::OnePercent).unwrap();
 //! assert_eq!(report.size, 8);
 //!
 //! let t_stat = report.test_statistic;
diff --git a/src/prelude.rs b/src/prelude.rs
index aabce2c..5691969 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -29,12 +29,12 @@ pub mod tools {
 
     /// Dickey-Fuller test
     pub mod dickeyfuller {
-        pub use crate::tools::dickeyfuller::constant_no_trend_test;
+        pub use crate::tools::dickeyfuller::dickeyfuller_test;
     }
 
     /// Augmented Dickey-Fuller test
     pub mod adf {
-        pub use crate::tools::adf::constant_no_trend_test;
+        pub use crate::tools::adf::adf_test;
     }
 }
 
diff --git a/src/tools/adf.rs b/src/tools/adf.rs
index 36e7694..c32cd7c 100644
--- a/src/tools/adf.rs
+++ b/src/tools/adf.rs
@@ -25,11 +25,12 @@ use crate::{tools, Error};
 /// - Constant and no trend model
 /// - Fixed lag
 /// - y must have strictly more than n + 1 elements.
-pub fn constant_no_trend_test<F: RealField + Scalar + Float>(
+pub fn adf_test<F: RealField + Scalar + Float>(
     y: &DVector<F>,
     lag: usize,
+    regression: Regression,
 ) -> Result<Report<F>, Error> {
-    let (delta_y, x, size) = tools::prepare(y, lag, Regression::Constant)?;
+    let (delta_y, x, size) = tools::prepare(y, lag, regression)?;
 
     let (_betas, t_stats) = ols(&delta_y, &x)?;
 
@@ -44,7 +45,9 @@ mod tests {
     use approx::assert_relative_eq;
     use nalgebra::DVector;
 
+    use crate::distrib::Regression;
     use crate::prelude::tools::dickeyfuller;
+    use crate::tools::adf::adf_test;
 
     #[test]
     fn test_t_statistics() {
@@ -63,7 +66,7 @@ mod tests {
             2.56363688,
         ]);
 
-        let report = super::constant_no_trend_test(&y, lag).unwrap();
+        let report = adf_test(&y, lag, Regression::Constant).unwrap();
         assert_eq!(report.size, 8);
         assert_relative_eq!(
             report.test_statistic,
@@ -88,8 +91,10 @@ mod tests {
 
         let y = DVector::from(y);
 
-        let report = super::constant_no_trend_test(&y, lag).unwrap();
-        let df_report = dickeyfuller::constant_no_trend_test(&y).unwrap();
+        let regression = Regression::Constant;
+
+        let report = adf_test(&y, lag, regression).unwrap();
+        let df_report = dickeyfuller::dickeyfuller_test(&y, regression).unwrap();
 
         assert_eq!(report.test_statistic, df_report.test_statistic);
         assert_eq!(report.size, df_report.size);
diff --git a/src/tools/dickeyfuller.rs b/src/tools/dickeyfuller.rs
index 83c4071..ce0afd0 100644
--- a/src/tools/dickeyfuller.rs
+++ b/src/tools/dickeyfuller.rs
@@ -29,9 +29,8 @@ use crate::Error;
 ///
 /// # Details
 ///
-/// Critical values for **model 1**  (constant, no trend): $\Delta y_t = \mu +
-/// \delta*y_{t-1} + \epsilon_i $ can obtained from
-/// `unit_root::prelude::distrib::dickeyfuller::model_1_approx_critical_value`.
+/// Critical values for can obtained from
+/// `unit_root::prelude::distrib::dickeyfuller::get_critical_value`.
 ///
 /// - If $t_{stat} < \mathrm{t_{\mathrm{crit}}(\alpha)}$ then reject $H_0$ at
 /// $alpha$ significance level - and thus conclude that the series is stationary.
@@ -42,7 +41,7 @@ use crate::Error;
 /// # Examples:
 ///
 /// ```rust
-/// use unit_root::prelude::distrib::AlphaLevel;
+/// use unit_root::prelude::distrib::{AlphaLevel, Regression};
 /// use unit_root::prelude::nalgebra::DVector;
 /// use unit_root::prelude::*;
 ///
@@ -60,13 +59,13 @@ use crate::Error;
 ///     -0.42968979,
 /// ]);
 ///
-/// let report = tools::dickeyfuller::constant_no_trend_test(&y).unwrap();
+/// let regression = Regression::Constant;
 ///
-/// let critical_value = distrib::dickeyfuller::constant_no_trend_critical_value(
-///     report.size,
-///     AlphaLevel::OnePercent,
-/// )
-/// .unwrap();
+/// let report = tools::dickeyfuller::dickeyfuller_test(&y, regression).unwrap();
+///
+/// let critical_value =
+///     distrib::dickeyfuller::get_critical_value(regression, report.size, AlphaLevel::OnePercent)
+///         .unwrap();
 /// assert_eq!(report.size, 10);
 ///
 /// let t_stat = report.test_statistic;
@@ -74,10 +73,11 @@ use crate::Error;
 /// assert!((t_stat - -1.472691f64).abs() < 1e-6);
 /// assert!(t_stat > critical_value);
 /// ```
-pub fn constant_no_trend_test<F: Float + Scalar + RealField>(
+pub fn dickeyfuller_test<F: Float + Scalar + RealField>(
     series: &DVector<F>,
+    regression: Regression,
 ) -> Result<Report<F>, Error> {
-    let (delta_y, y_t_1, size) = prepare(series, 0, Regression::Constant)?;
+    let (delta_y, y_t_1, size) = prepare(series, 0, regression)?;
 
     let (_betas, t_stats) = ols(&delta_y, &y_t_1)?;
 
@@ -106,7 +106,7 @@ mod tests {
         let delta: f32 = 0.5;
         let y = gen_ar_1(&mut rng, n, 0.0, delta, 1.0);
 
-        let report = constant_no_trend_test(&y).unwrap();
+        let report = dickeyfuller_test(&y, Regression::Constant).unwrap();
 
         let critical_value =
             match constant_no_trend_critical_value(report.size, AlphaLevel::OnePercent) {
@@ -127,7 +127,7 @@ mod tests {
         let delta: f32 = 1.0;
         let y = gen_ar_1(&mut rng, n, 0.0, delta, 1.0);
 
-        let report = constant_no_trend_test(&y).unwrap();
+        let report = dickeyfuller_test(&y, Regression::Constant).unwrap();
 
         let critical_value =
             match constant_no_trend_critical_value(report.size, AlphaLevel::OnePercent) {
@@ -148,7 +148,7 @@ mod tests {
         let delta: f64 = 0.5;
         let y = gen_ar_1(&mut rng, n, 0.0, delta, 1.0);
 
-        let report = constant_no_trend_test(&y).unwrap();
+        let report = dickeyfuller_test(&y, Regression::Constant).unwrap();
 
         let critical_value =
             match constant_no_trend_critical_value(report.size, AlphaLevel::OnePercent) {
@@ -169,7 +169,7 @@ mod tests {
         let delta: f64 = 1.0;
         let y = gen_ar_1(&mut rng, n, 0.0, delta, 1.0);
 
-        let report = constant_no_trend_test(&y).unwrap();
+        let report = dickeyfuller_test(&y, Regression::Constant).unwrap();
 
         let critical_value =
             match constant_no_trend_critical_value(report.size, AlphaLevel::OnePercent) {
@@ -184,7 +184,7 @@ mod tests {
     #[test]
     fn no_enough_data() {
         let y = DVector::from_row_slice(&[1.0]);
-        let report = constant_no_trend_test(&y);
+        let report = dickeyfuller_test(&y, Regression::Constant);
         assert!(report.is_err());
     }
 
@@ -194,7 +194,7 @@ mod tests {
 
         let y = DVector::from(y);
 
-        let report = super::constant_no_trend_test(&y).unwrap();
+        let report = dickeyfuller_test(&y, Regression::Constant).unwrap();
 
         assert_eq!(report.size, 9);
     }