diff --git a/01_pytorch_workflow.ipynb b/01_pytorch_workflow.ipynb
index bbb84bac..05a709a6 100644
--- a/01_pytorch_workflow.ipynb
+++ b/01_pytorch_workflow.ipynb
@@ -220,6 +220,8 @@
     "end = 1\n",
     "step = 0.02\n",
     "X = torch.arange(start, end, step).unsqueeze(dim=1)\n",
+    "#y = MX + b used formula",
+    "ref: https://www.wallstreetmojo.com/regression-analysis-formula/ \n",
     "y = weight * X + bias\n",
     "\n",
     "X[:10], y[:10]"
@@ -1658,6 +1660,8 @@
     "\n",
     "# Create X and y (features and labels)\n",
     "X = torch.arange(start, end, step).unsqueeze(dim=1) # without unsqueeze, errors will happen later on (shapes within linear layers)\n",
+    "# y = MX + b used formula",
+    "# ref https://www.wallstreetmojo.com/regression-analysis-formula/ \n",
     "y = weight * X + bias \n",
     "X[:10], y[:10]"
    ]