diff --git a/core/data-formats/netcdf-cf.ipynb b/core/data-formats/netcdf-cf.ipynb
index 2abb46f88..d69d572a2 100644
--- a/core/data-formats/netcdf-cf.ipynb
+++ b/core/data-formats/netcdf-cf.ipynb
@@ -983,7 +983,6 @@
     "\n",
     "- [CF Conventions doc (1.7)](http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/cf-conventions.html)\n",
     "- [Jonathan Gregory's old CF presentation](http://cfconventions.org/Data/cf-documents/overview/viewgraphs.pdf)\n",
-    "- [NASA ESDS \"Dataset Interoperability Recommendations for Earth Science\"](https://earthdata.nasa.gov/user-resources/standards-and-references/dataset-interoperability-recommendations-for-earth-science)\n",
     "- [CF Data Model (cfdm) python package tutorial](https://ncas-cms.github.io/cfdm/tutorial.html)\n",
     "- [Tim Whiteaker's cfgeom python package (GitHub repo)](https://github.com/twhiteaker/CFGeom) and [(tutorial)]( https://twhiteaker.github.io/CFGeom/tutorial.html)\n",
     "- [netCDF4 Documentation](https://unidata.github.io/netcdf4-python/)"
@@ -1013,7 +1012,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.9"
+   "version": "3.11.9"
   }
  },
  "nbformat": 4,
diff --git a/core/datetime/datetime.ipynb b/core/datetime/datetime.ipynb
index 4ce443e78..400f4d153 100644
--- a/core/datetime/datetime.ipynb
+++ b/core/datetime/datetime.ipynb
@@ -351,7 +351,7 @@
     "\n",
     "In these examples, we will look at current data pertaining to coastal tides during a [tropical cyclone storm surge](http://www.nhc.noaa.gov/surge/).\n",
     "\n",
-    "The [lunar day](http://oceanservice.noaa.gov/education/kits/tides/media/supp_tide05.html) is 24 hours and 50 minutes; there are two low tides and two high tides in that time duration. If we know the time of the current high tide, we can easily calculate the occurrence of the next low and high tides by using the [timedelta class](https://docs.python.org/3/library/datetime.html#timedelta-objects). (In reality, the *exact time* of tides is influenced by local coastal effects, in addition to the laws of celestial mechanics, but we will ignore that fact for this exercise.)\n",
+    "The [lunar day](https://tidesandcurrents.noaa.gov/glossary.html#lunarday) is 24 hours and 50 minutes; there are two low tides and two high tides in that time duration. If we know the time of the current high tide, we can easily calculate the occurrence of the next low and high tides by using the [timedelta class](https://docs.python.org/3/library/datetime.html#timedelta-objects). (In reality, the *exact time* of tides is influenced by local coastal effects, in addition to the laws of celestial mechanics, but we will ignore that fact for this exercise.)\n",
     "\n",
     "The `timedelta` class is initialized by supplying time duration, usually supplied with [keyword arguments](https://docs.python.org/3/glossary.html#term-argument), to clearly express the length of time. The `timedelta` class allows you to perform arithmetic with dates and times using standard operators (i.e., `+`, `-`, `*`, `/`).  You can use these operators with a `timedelta` object, and either another `timedelta` object, a datetime object, or a numeric literal, to obtain objects representing new dates and times.\n",
     "\n",
@@ -554,7 +554,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.9"
+   "version": "3.11.9"
   }
  },
  "nbformat": 4,